People that refused religion have killed more people than all religions have so I think your the one with the fallacy dumbass.
The fallacy, my dear sir, is the basic idea of comparing murders based on religion, against those committed devoid of such a basis.
You're presuming atheist atrocities "out-perform" atrocities based on religion, when the simple fact is an atrocity needs neither basis - instead, only that of the twisted (or 'anti-social', if such fallacious logic still rules this discussion) individual's (and those he/she have brainwashed) personal beliefs to cause such suffering.
Religion, sex, death, genocide, etc. etc. etc. - ALL CIRCUMSTANTIAL. No one has any right whatsoever placing blame on a reason that can be used universally.
Investing some time in reading the book, 'A Brief History of the Paradox', may serve many here as good reference material when dealing with similarly pointless banter.
People that believe in a peaceful religion tend to not do shit that isn't peaceful while people that have no moral backing don't have any real restrictions besides personal which is very subjective.
The difference is Islam, of course. Why? Because Islam has violence directives right along with peace directives right in its holy writings.
I don't consider Islam a religion of "peace". no matter how many times they play that narrative actions speak louder then words.