From the other website:

Because of the relatively small concentrations required to exterminate humans as opposed to lice, and because of the far shorter exposure time required, the HCN in the gas chambers used to kill humans hardly had time to form chemical compounds on the walls.

But even in low concentrations this chamber was allegedly used almost non-stop in order to account for all the deaths; even the 250,000 deaths in 1943 claim would require 700 people to be killed a day or 30 and hour -- these people mean to suggest that even in low concentrations no residue would form on the walls with an average of 30 deaths an hour?

the extermination chambers were destroyed. Clearly, their walls were exposed to the elements for forty-five years, which would certainly effect the validity of the samples taken. (The ruins of Krema II are covered with about three feet of water during certain periods of the year, and HCN compounds would eventually dissolve under such conditions. Nonetheless, so many gassings occurred there that some of the compound did remain).

Right here they admit that the sheer frequency of gassing would be sufficient to leave residue, and they claim it is exposure to elements of torn down structures alone that reduced the levels of residue. But not just torn down structures were analyzed, but structures standing in the same condition as the delousing chambers, and the residue remains negligible. In fact the page goes on to reference this argument:

The deniers often claim that the gas chamber in Krema I was left intact, and therefore its walls were not exposed to the elements. Curiously, they also make great issue of the fact that Krema I was converted into an air-raid shelter, and then rebuilt by the Soviet Army, after the liberation of the camp, to reproduce its original shape, saying that it has been used to mislead the public, who were told that people were gassed in the building.

I haven't heard of the Soviets tearing it down and re-building it in the exact same shape; I find this improbable. But if it were the case then I don't see how Holocaust acceptors can use the Krema I building (the only still standing "crematorium" in Auschwitz if I'm not mistaken) as evidence of gas chambers! It is not that either position weakens the deniers' arguments; it weakens the acceptors' arguments whatever the case. If the building remained standing and was not exposed to the elements, and the residue levels remained so negligible, then that shows that that major part of Leuchter's Report is not in fact debunked. But if the building was torn down and rebuilt, then what basis do the acceptors have for pointing to gas chambers in the first place?

The modification consisted of essentially removing some partitioning walls inside the gas chamber, which were added as a common feature of bomb shelters.

At least here they acknowledge the torn down walls instead of pretending they didn't exist. Strange to install walls in a building allegedly built for gassing people only to tear them down before the room is used.

the gas chamber of Krema I was used only for a short time, before the conversion. This, and the fact that "only" about ten thousand people were murdered within it, compared to three-hundred-fifty-thousand and four-hundred-thousand in Kremas II and III, explains why relatively small amounts of cyanide compounds remain. The other Kremas were destroyed by the SS prior to the Soviet liberation.

Oh how convenient! The only crematorium still standing was only used to kill 10,000 people (a number that actually aligns with Soviet records, except these deaths were results of typhus and other causes, not gassing) while the other two crematoria that were destroyed are where the VAST MAJORITY (+350,000) of Jews were allegedly killed.

Holocaust denial asserts that the doors of the "alleged" gas chambers were much too weak to withstand the pressure of people trying to escape death from inside the chambers.

Since none of the Kremas remained in their original state (Bunker I & II and Kremas II,III,IV and V destroyed, and Krema I modified) there is no physical evidence as to what the doors of the extermination gas chambers looked like

Again this word of Krema I being heavily modified is news to me; if other, more sturdy doors were in fact used then that is one less strangeness for me to dwell on. But the idea that this structure was rebuilt I find improbable, pointless, and absurd, and I feel that it's existing in a non-original state does more harm to the acceptor arguments than the denier.

In the course of this final solution of the European Jewish Problem, approximately 11 million Jews are involved. They are distributed among individual countries as follows:

Here they tackle the "denier claim" that there weren't enough Jews to possibly kill 6 million. I'll take a moment to say that I am skipping over a number of points that I say this webpage does successfully debunk, but they are never points I have cited or heard before -- and for the most part they are minor points. So here they say that there were 11 million Jews throughout Europe and the USSR at the time of the war, and 5 million of them were from the USSR. I've never denied any of Stalin's crimes because there is plentiful evidence for them. Hitler did not operate camps in what was the USSR before or during the war, and so I fail to see how 5 million of those Jews can be attributed to him. Did 100% of the remaining Jewish population get killed by Hitler, despite the total numbers not adding up to anything close to that? The second highest number after the 5 million from the USSR is 2.4 million from Poland -- a nation Stalin invaded! Also this page "deleted values from many countries for brevity" so I can't even see where the rest of the Jews really came from -- others numbers are sub-500,000.

There's more but I can't sift through it all now. This page successfully debunks a large number of lesser important claims that were allegedly made in the Leuchter Reports, but I think the largest claims were debunked with the least success. Let us say that I think more discussion and debate could be had on that specific topic. But there are countless other inconsistencies even beyond the contents of Leuchter's reports.

Have you seen the number of appearances of the figure "6 million" with reference to Jews prior to WWII? I'm sorry, friend, but it still seems to me that the Holocaust narrative is rampant with inconsistency and false claims. Did Hitler hate Jews? Certainly. Could he have informally asked for the deaths of those that were in the camps? Of course. Was he a perfect man? Certainly not. But the numbers are wildly higher than most evidence seems to suggest.

I'm going to read through the page this website links to that debunks the Leuchter Report specifically in more detail. Concerning the contents of your link itself, here is the article's conclusion:

Drawing moral equivalences are problematic as the existence of other horrible crimes do not negate the crimes of the Nazis. Holocaust revisionists are actually Holocaust deniers as they reject many of the core aspects of the mainstream historiography of the Holocaust. Like creationists abuse the internal scientific debate between phyletic gradualism and punctuated equilibrium as if it was a debate about the validity of common descent, Holocaust deniers abuse the internal historical debate between intentionalists and functionalists in an attempt to spread uncertainty and doubt regarding Holocaust history at large by quoting historians out of context.

The swimming pool at Auschwitz was a water reservoir for firefighting and pool for SS men and privileged prisoners. The surplus of Zyklon-B left over after delousing at Auschwitz was around 3-6 times more to kill the estimated quarter of a million people during 1943. The claims of the pseudoscientific Leuchter report has been disproved: in reality, the concentration of hydrogen cyanide was too low to be explosive, diesel fumes contain carbon monoxide which can kill people, lice are more resistant to hydrogen cyanide than humans and the walls of the homicidal gas chambers has been exposed to the elements for many decades.

While a single eyewitness might be unreliable, multiple independent eyewitness accounts corroborated by physical evidence are very reliable. By failing to make this key distinction, Holocaust deniers are abusing and distorting cognitive psychology. Demographics and estimates of the number of people killed independently converge, making demographics estimates robust. The word “ausrotten” means exterminate when applied to living things, and no amount of rationalizations by Holocaust deniers will change this was some Nazis spoke of “ausrotten” bacillus or tuberculosis in the same speech and document as “ausrotten” the Jews. No serious person can claim that the Nazis wanted to put tuberculosis bacteria on trains and deport them out of the country.

This summarizes all the points made in the article. I'll go through them one by one and then get back to you once I've read through the thorough Leuchter Report debunking.

• moral equivalences are not an argument; I agree.
• Holocaust revisionists are actually Holocaust deniers; semantics and terminology, irrelevant.
• Holocaust deniers abuse the internal historical debate between intentionalists and functionalists in an attempt to spread uncertainty and doubt regarding Holocaust history at large by quoting historians out of context; this is a sweeping generalization fallacy and largely meaningless towards debunking individual claims.
• The swimming pool at Auschwitz was a water reservoir for firefighting and pool for SS men and privileged prisoners; the article states no documentation proving this, and it is a minor issue anyway. I'd be curious to see what the authors of this article would say about the movie theatre indoors, which Jews had access to and enjoyed according to certain Jews who lived in Auschwitz.
• The surplus of Zyklon-B left over after delousing at Auschwitz was around 3-6 times more to kill the estimated quarter of a million people during 1943; this section of the article was amusing. They make several estimates about what would be necessary for delousing train yards and barracks and clothings etc and arrive at a figure for leftovers which they then properly demonstrate could be used to kill 250,000 people. They argue the large amount of Zyklon-B sent to Auchwitz (the majority of it distributed at all) are indicative of using the surplus to kill. Yet only a fraction of the totals remain after their estimates "to be used for killing" -- that fraction is the safety buffer. It's basic engineering. Don't sent only what you'll need, send more than you could possibly need in case anything goes wrong. Since more Zyklon-B is needed for pests than people, as the article correctly states, that remaining fraction becomes considerably less of a "surplus" when it is recognized for the intended use of delousing.
• The claims of the pseudoscientific Leuchter report has been disproved; I'll return to this point after reviewing the other website.
• While a single eyewitness might be unreliable, multiple independent eyewitness accounts corroborated by physical evidence are very reliable; what physical evidence? It omits that part. And what of the large number of eyewitness testimonies that contradict the Holocaust that are supported by physical evidence. I mean the overhead airplane photographs where no extermination or signs of extermination are visible; the claims of a lack of visibility or awareness of any gas chambers, and pre-1945 photographs of Auschwitz without the useless chimney sitting beside the "gas chamber"; the insufficient doors ways for containing the gas; the lack of mass graves aligning with the number claimed dead; the number of dead in Auschwitz changing drastically as the years go on, decreasing from 4 million to a few hundred thousand as is accepted today, without the 6 million figure ever going down? That physical evidence aligns much better with the anti-Holocaust testimonies than any evidence in support of the claim.
• The word “ausrotten” means exterminate when applied to living things; the article admits it can be used to mean "uproot" as well, and yet they dismiss this as absurd, whereas I think it fits the situation perfectly. The Germans did want to uproot the Jews -- get them out of Europe. And they began methods to do so and would likely have had more success if not stopped with Britain and France's declaration of War.

That's all the article really supplies; it seems their debunking is easily debunked itself. And it mentioned nothing about how convenient it is that THE ONLY DEATH CAMPS WITH GAS CHAMBERS ARE CAMPS THAT WERE WITHIN SOVIET-OCCUPIED TERRITORY AFTER THE WAR. No mention of the evidence that the Auschwitz chimney was added after the war, no mention of the obvious holes in the Auschwitz gas chamber floor where plumbing (bathroom equipment) had once been, no mention of the marks on the wall clearly indicative of walls having been torn down, no mention of the total lack of formal calls from Hitler to exterminate any group despite the number of documents seized, no mention of the role Stalin played in covering up his own crimes by trying to distract the world with Hitler, no mention of the role Stalin played in killing millions in Poland -- deaths often attributed falsely to Hitler. No mention of so many crucial points! Half this article rambles on about how morally and factually superior Holocaust acceptors are to Holocaust deniers. A pitiful article all things considered.