What primarily seems to motivate atheists isn't rationalism but anger I have found this to be true. I know some very angry atheists. And not just angry, but extremely intolerant. They seem to think that if they don't believe in God, no one else should either. And they should never have to listen to mention of God in public.
Assume there are two groups of atheists. Group one is angry and rude in asserting their atheism while group two is tolerant and considerate of the feelings of others. You would likely notice only members of group one.