Fundy atheists maybe, but not because they're atheists. They'd be 'fundy' about other things. All you'd be describing is 'Someone who is a fundamentalist about X and also happens to be an atheist', because correlation and causation should not be confused. I don't see what's the point of saying "'fundy' atheists" when they could just as easily be fundy theists, it's just that they don't believe in God. It's got nothing to do with them being atheists.
EvF
EvF