Okay, I've been thinking about it, and have come to the following conclusion. Maybe I'm wrong; it wouldn't be the first time. But here's an analogy that makes sense to me:
Sexual orientation (i.e. sexual preference) seems to me to be inborn. We don't choose who we're sexually attracted to. Sexual behavior is clearly a choice. We either choose to act on our feelings of sexual desire or we don't. And obviously, this goes for everyone, homosexual or heterosexual.
I kind of equate belief in God with sexual orientation. It seems to be something you can't talk yourself into or out of. I don't choose to believe in God, I just do. I couldn't stop believing no matter what happened in my life. I could get frustrated wondering why He does some of the things He does, but no matter what, I'll always believe. There is just something inside of me that says He's there. I have known atheists who would really like to be able to believe in a God, but just can't will themselves to do so. No matter what happened in their lives, they could not attribute any of it -- good or bad -- to the existance of a Higher Being.
On the other hand, I have more or less chosen which religion to follow. It was a conscious decision, based on the teachings of the various religions there are to choose from. While I doubt I will ever leave Mormonism, it is conceivable that something in my life could convince me otherwise. Who knows, I may die a Buddhist. I see sexual behavior in much the same way. We choose to be sexually active or to remain celibate. Homosexuals don't, in my opinion, choose to be attracted to people of the same sex, but they choose whether or not to act on their feelings.
Here's where it gets back to the OP. I can understand why a homosexual Christian would choose to reject Christianity. I don't understand how a homosexual Christian could choose to reject God. Anyway, I don't know if that makes any sense at all. It's just something that has been on my mind.