I can't tell you what it means, yet. In all honestly, I am thoroughly confused and disturbed by some of the images, comments and the amount of sharing on the topic I'm seeing online. It started just as a simple theory, that somehow Pizza wasn't in reference to pedophilia (not necessarily, anyways), but rather it had something to do with the Occult. So, I tried the Dark Web, but Tor is too slow. I decided to stick to the ClearNet, and simply do some Google searches. Search almost anything related to the Occult: "Occult Pizza", "Satanic Pizza", whatever, it all turns up the same very weird result, that there is undeniably some connection between more than literally eating pizza, and Satanism. I haven't been able to narrow down the secret relationship the two have that people don't seem to discuss openly, but such is the Occult world. Secretive. Try the search. Here's a taste: https://www.tumblr.com/search/satanic+pizza