Militant atheists (the sincerely anti-theists) have been guilty of more deaths in one half century than theists have in the entire written history of mankind.
They don't kill 'in the name of atheism' (though that's the bottom line). They kill 'because you are a theist and don't deserve to live.'
they killed other people for other reasons, too, of course, but they killed people. Lots of 'em. ...and the fact that they didn't have a God to explain things to was part of the reason they could.
We ARE talking only about the 'militant' atheists, though, rignt? Personally, I figure that if it walks like a religion, and talks like a religion, it's a religion...even if the basis for it is 'there is no God and that is a truth that we can force others to acknowledge" or "there is a god, and He is Who we say He is, and we can force our beliefs on others." When the results of a belief are the same either way.....I honestly don't see much difference.