A lot of Christians are creationists just because they never realized that they were allowed to believe that evolution happened and still be Christians. At an event a few months ago (I forget the specifics, sorry) there were a bunch of religious speakers talking about how to reconcile Christianity and evolution, and the crowd of mainstream religious folks were just blown away. The prevailing sentiment was "Wait, that's an option?"

In a similar way, the most common argument I've heard for why people are against homosexuality is "Well, I'm a Christian." As if this obviously implied that they had to disapprove of the queers. I imagine that a lot of this is just simple ignorance: a lot of people don't know that being non-bigoted is even an option for them.

Maybe. Personally, I tend to go for more of a scorched-earth approach, but we need more than one approach to persuasion here.