And don't forget that if you're not into the Chicks, you can always just leave during their set - take a bathroom break, get a drink, etc. That's what people did when JD and the Straight Shot opened for Don!
I'm one of those who finds it tiresome when singers start to preach at me from the stage. Some of these stars see it as their duty to try and evangelize the masses, I guess, but I seriously doubt any audience member ever changed their opinion due to a sermon-ette at a concert. Instead, the audience members who agree with you cheer, and the audience members who don't agree with you feel dissed and maybe even boo. Not much is accomplished other than fan alienation. The only positive, really, is for the rock star: he/she gets to feel that sense of self-satisfaction that comes whenever one voices one's opinion. (I should add here that some fans do feel personally validated if their beliefs align with their favorite rock star's. I wouldn't call that a "positive" though - it's rather pathetic.)
That said, if the music is good, I'll stay in my seat. Plus, it's impolite to boo.
And I'll stay in my seat to watch the Dixie Chicks.