Everyone has an idiot button. Everyone. I think even Penn and Tiller covered that (which is funny because one of them has an idiot button, too. I just forget which, off the top of my head.)
I do like the part where someone mentioned (I think it was Lithp?) that this deals with groups, not individuals. Because I can understand there being a larger percentage of atheists that are smart than a percentage of, say, Christians.
As far as individuals go, I've met some atheists who took the label simply because they want to proclaim that they're smarter than everyone else.
Or as we should probably start calling them, "chageneists"