Well, there are tolerance on both sides. Homosexuals want to be tolerated, yet they don't tolerate people who think what they do is wrong.
Personally, I can't seem to figure out what causes homosexuality. More and more I think people are born that way, but i could be wrong. I do know that despite what the religious right will tell you, they can't change their sexual preference on the drop of a hat. Even the so-called "Christian converted homosexuals" still have attractions to other men, they just don't act upon them.
My best friend in tech school turned out to be gay, and he couldn't help it. He had effeminate traits growing up, and I suspected he was the whole time I knew him, and when he came out of the closet on graduation night, although it felt awkward, it was nothing I didn't know before.
One thing that is interesting is how most homosexuals I've known have a higher income than the norm, or they grew up having been spoiled by their parents. This isn't always the case, but it has been for many of the homosexuals I've known, and I do know several from my college.