I don't see how sexual orientation would put people in categories at all. In fact, I don't even like the expression "sexual orientation", I usually say sexual preference. I don't think your sexual preferences define you entirely as a person any more than I think your favorite music defines you. I see it entirely as a matter of taste. It's possible to like metal and hip hop at the same time, just like it possible to like one and to dislike the other, or to like both but to prefer one, I see sexual preferences in the same way. Being attracted be a sex is not a choice, just like you can not chose to like or to dislike this or that music, but you can still chose not to act on it, in both cases. And, even though I don't like hip hop, I would still think it's wrong to ban hip hop, and so in the same way, even if I was 100% straight, I would still find it wrong to persecute GLBT people.
The evidences that homosexuality is genetic is actually pretty damn weak, although I still agnostic on the matter, but it doesn't matter to me. If homosexuality is an acquired behavior, as long as we don't have any reason to say gay sex is bad, gay sex is not bad. If homosexuality is innate, if we had legitimate reasons to say it's wrong, it would still be wrong. So it's completely irrelevant whether it comes from nature or nurture. The only thing that matters is that there is no legitimate reason whatsoever why homosexuality would be wrong. There is no victim, and the only harm it causes that wouldn't also be caused by straight sex wouldn't exist if it wasn't for homophobic bigots.