Being gay is a fetish.

[Esquilax]

Sure is. But as I've given evidence, such as twins studies, for my position, I'm not doing that.

The twin study, at best, rules out a purely genetic predisposition, it's not evidence that homosexuality is a choice or a lifestyle. Purely genetic/completely conscious choice is a false dichotomy, especially in light of the fact that, most likely, it's due to a combination of factors. But the simple lived experience of other people completely invalidates this claim that it's some conscious choice and nothing more; for all your talk about evidence you're certainly willing to completely ignore that whenever it's brought up.

Further, Brian said that I have no scientific understanding of reality regarding human sexuality, so it's perfectly legitimate to ask to see the scientific evidence which I supposedly don't understand. 

What's not legitimate is you deciding that your wild, only partially justified assertion stands until proven wrong, especially when the science itself has not come to a conclusion yet. Study is still ongoing, even your twins studies have additional factors that could explain the results due to the mechanisms of how twins form, and so it is completely ludicrous for you to assume that your position is somehow the default.