Interesting - So, basically, homosexuality could be labeled as wrong if it detracted from someone else's life.
I just had an idea about why homosexuality could be fundamentally wrong in Christianity. I'll try to explain it with the hopes that it'll be insightful rather than insulting or demeaning - It's an attempt to play along with the premise/conclusion game.
Family is a large part of most Christian communities, and even the teachings in the bible. The ability to procreate is considered sacred, and so should not be abused. If you believe that one purpose of a family is to give more people the opportunity to come to earth, learn, and grow (Assuming that our being here is part of God's plan), then homosexuality or even celibacy would be wrong. If you also believe that families can continue to grow after resurrection, then even someone who doesn't have the ability to procreate in this life would have the responsibility to be in a position to be able to do so in the next; so someone who's sterile can't become homosexual by saying that they can't have children anyways.
This is, of course, laying aside the whole self-control and mastery of passions and desires bit, which is also a big part of Christianity.
In the end, whether or not homosexuality is acceptable is dependent on your belief in God and/or your view of the importance of a family and bringing life into existence, whether in this life or the next. So, to most Christians, homosexuality could/should be seen as less of an act of rebellion as failing to acknowledge the importance of families and giving others the chance to come to earth. Thus being a homosexual doesn't automatically make you an "evil person".
I hope that makes sense. I didn't think about it too much - It sort of popped into my head. I'm not going to claim ownership of or advocate the idea until I can think about it some more (And with school starting tomorrow, I probably won't have time to explain that, not to mention the inevitable misunderstandings :\ ).
And please don't take it out of context - I'm really trying to open up understanding by thinking about what could be causing people to detracting homosexuality. I'm not trying to tell people that they're wrong and need to mend their ways - In fact, I'm presenting more of an idea than a personal opinion! Whether or not it's the reason behind the belief that "homosexuality is bad" is still up in the air (To me).
Regardless of where my opinion goes, my previous statements on freedom of choice still stand, of course. As long as something doesn't affect or harm me, I'm not going to get all worked up about it.
If you don't remember them or haven't read said opinions and don't understand the above line, feel free to browse around for them in this thread. I think it sums up what a large portion of Christians think.