Those who are political about their atheism (have a point to
   prove to the world), are UBER moral to try to prove that "see
   guys, no God needed? See? SEEEEEEEEE?" But people who are
   atheist just because are likely no morally different than
   anybody else. Of course, if someone's atheist 'cause they hated
   their upbringing MIGHT be amoral simply because they hated their
   upbringing.