There's a standard Internet phenomenon (I generalize) of a Sneer Club of people who enjoy getting together and picking on designated targets. Sneer Clubs (I expect) attract people with high Dark Triad characteristics, which is (I suspect) where Asshole Internet Atheists come from - if you get a club together for the purpose of sneering at religious people, it doesn't matter that God doesn't actually exist, the club attracts psychologically f'd-up people.