It's most likely because the people who post on these forums are too mature to be squeeing rabid fangirls that leap at the thought of males going at it.
Personally, (I'm sorry, I know you guys are close to my best friend [Irene] but I'm going to be a dick) I think that yaoi gets old, and fast. Thinking that fangirls are going to loyally glue themselves to you just because you happen to be a gay couple, you really do have another thing comming.
The idea, also, of trying to create a fandom for said fangirls, is unheard of and almost, to a degree, selfish.
I say that if you want to create a fandom, don't create a thread, for christ's sake, create a website, a place where two guys violently making out is less of an everyday sight.
THAT IS ALL
(and I'm sorry, don't blame Irene, she's not a dick, I am)