According to what I have seen, sites like this and Snopes are often politically biased. In this case, the only proof is a disavowal from GSUSA. Why would I believe them?
Well for fairness sake one ought to note that the GSA officially disavowed them. One hopes that however libertine they have gotten, they are not yet at the level of Baghdad Bob about it.
Actually, its very simple. If this was a brochure, then there should be a copy of it. If you can find one, I’ll believe it. The only “Proof” is actual evidence. Not something someone wrote on the internet.