I have found some interesting prior uses of the triangle logo within their correct context before it became more widely known through Pizzagate (and via the FBI 'childlover' document)

Have a look at 5:43 https://www.youtube.com/watch?v=7cKRy2WJ_tw&t=343s

Having a look at the website referenced in the video through Wayback machine, they used this logo in 2002 http://web.archive.org/web/20021129152113/http://boylover.net/

We have the FBI document released through WikiLeaks as a primary source, but I think these examples provides further corroboration as we see the logos prominently in context of very definite illicit activity and not necessarily used as a signalling device.

To anyone thinking it's just a fairly benign logo, think again...