I graduated from a small rural town high school. Population of about 400 or so, mostly farms. I always hated seeing people getting picked on, so the guys who would get picked on for not being as masculine as the others became my friends because I routinely stuck up for them. A couple of them came out to me, and I assure you that it is not a choice, because if it were, those guys would have chosen to be straight in a heartbeat. They lived in fear that someone would find out they were gay and might be physically harmed by the less tolerant people in the school (there were a lot of them...remember, this is a farm town).
Yes, acting on your feelings is a choice, but a homosexual has just as much of a right to act on their feelings as any of you do. It's not "wrong" or "inhuman", because if it was, it wouldn't happen. Every time someone uses the slippery slope argument of "Well if we accept that, what stops them from marrying animals?" it makes me want to throw them out a window. It's inhuman to be so intolerant of something that doesn't affect you in any way, and to be so irrational as to make such an argument.