Stalin and Hitler were men of faith
"Without God, we end up like atheists Stalin and Hitler." Asinine beyond reason (though not beyond belief), yet the line just won't die. (Never mind the additional ridiculousness that Hitler, like most Nazis, was a Christian.) From big-name cardinals to school-board creationist nut cases, the "faithful" love to toss out Stalin, Hitler, Pol Pot, and their ilk as the end result of losing religion.
Pretending for a moment that Hitler wasn't a Christian, let's say that these dictators indeed weren't religious. Fine. But while they're not religious, they were all men of faith. Overpowering, self-righteous, unwavering faith.
Stalin had no proof that Communism was superior and would crush capitalism; he took that belief on faith. Hitler's fantasies about Jewish conspiracy and the superiority of the Reich? Again, no evidence, just faith of a strength on par with that of Biblical prophets. Mao Zedong justified his catastrophic Great Leap Forward not with empirical backing, but monstrous faith that it would work miracles.
The above is why I'm not so keen on the forces of reason targeting religion as an enemy of humanity. "Religion" is undefined; the fact that there's an infinite number and variety is what lets the God-smacked dodge bullets in debate, continuously claiming "well, you're addressing that guy's religion, not my religion". Religion can be anything, including the unassailably vague (and harmless!) "sense of awe and inspiration" many things make us feel. And, of course, defenders of religion will play the tired Stalin card again and again, pretending each time that it wasn't thoroughly crushed a million times before. (In debates, it's the God-lovers' version of filibustering: waste all the alloted time so the side of reason barely gets a new word in. They win by default!)
But if we make faith – belief without evidence – our targeted enemy, the crosshairs point directly at Stalin, Hitler, and Pol Pot. They acted on faith, not evidence, with the horrific results we see. The "argument by Stalin" tactic turns against the God-smacked.
Stalin. Hitler. Pol Pot. Mao Zedong. Men of faith.
Shout it from the mountain tops.
(Note: See a more detailed, thoughtful take on the topic at Sorry, You Get These Guys Too: Or, The Irrational Faiths of Hitler, Stalin and Mao.)