Highly doubtful - they are fighting any notion that (they perceive) even remotely conflicts with their own beliefs. Among many with whom I've spoken, I have never encountered a single biology teacher who a) is remotely as hostile toward religion as religious zealots are toward evolution, or b) feels compelled to teach "atheism" in the classroom. Teaching evolution and teaching the view that there is no God are two completely different animals (This misconception is what drives the 'religiously enthusiastic' people in Kansas insane). I have, on the other hand, found many strong proponents of evolution (by natural selection) who still more or less independently maintain their own religious beliefs. Ken Miller is an excellent example.

Second, when the author compared gravitation to evolution, he was referring to the sense in which evolution is a flat fact, just like gravity. Many of the school board members who oppose evolution in the classroom actually believe that evolution (regardless of the mechanism) didn't/doesn't happen at all. Such a position is just as ludicrous as believing the world to be flat, or that there is no gravity.