For one thing, splitting off from the Catholic Church pretty much makes you "Protestant" by definition, whatever you might like to call yourself. If one is committed specifically to Catholicism, that's a problematic step.
Yeah, I'd rather not get into the debate over who gets to call themselves what. Besides, Catholic means "universal". While the Roman Catholic Church is the largest denomination, I wouldn't call them universal.
For another thing, maybe there's some tension between their beliefs and the Church's doctrines that they just don't feel like resolving. For better or worse, where birth control is concerned a lot of Western Catholics seem able to live with pretty fundamental cognitive dissonance between their opinions and the Church's established stance. One way or the other, grasping the nettle would exact some costs that many people don't feel like paying.
Maybe I'm just weird that way. When my old church basically said homosexuals burn in hell, and anyone claiming otherwise was serving the devil, I left and never looked back. Eventually I left the faith altogether but that's a different story.
Finally, most Christian churches are packed to the gills with people who—gay, straight, or otherwise—are sinners by their churches' standards. Even if Catholic teaching on homosexuality is 100% correct, I doubt that from God's viewpoint I'd stand any better than the average gay congregant, or be considered less fundamentally broken in my own particular ways. We've all got issues.
I've heard the "we're all sinners" argument before. But it's my impression that non-heterosexuality is generally treated as a sort of "super-sin", receiving far more attention and condemnation than its fair share. Don't believe me? Compare how much religious opposition there is to same-sex marriages (even when performed by other religions or as completely secular) as opposed to how much religious opposition there is to divorce. The Bible could be said to argue against both, but the former in this day and age is treated as a much bigger deal.
And that's not even getting into the fact that some Christians (or if you prefer, people who identify themselves as Christians) don't believe non-heterosexuality is wrong in and of itself. And I just really don't understand why said people would choose a religious group that not only believes the opposite, but actively campaigns against their religious freedom as the Catholic hierarchy is known to do.
edited 3rd Jan '13 8:13:26 AM by Morgikit
"Morgi's thing is political activism, furriness, and being fudging adorable." - Enkufka