Nevertheless, they did exist. I have a Russian friend who did "Atheism class", who now has a PhD in Mathematics. The irony was that it was the atheism class which made her believe there was a God. I too was stunned when she told be about the class, as it made no sense, but she insisted that it was a class dedicated to teaching children that there was no god, and used evolution to try and prove it. It sounded like precisely the sort of thing that Richard Dawkins was trying to promote with his atheist summer camps for children.
You can shift the goal posts and do as much mental gymnastics as you like; the fact remains that the worst atrocities in history were perpetrated by regimes who asserted the God did not exist.
Aleksandr Solzhenitsyn:
Over a half century ago, while I was still a child, I recall hearing a number of old people offer the following explanation for the great disasters that had befallen Russia: "Men have forgotten God; that's why all this has happened." Since then I have spent well-nigh 50 years working on the history of our revolution; in the process I have read hundreds of books, collected hundreds of personal testimonies, and have already contributed eight volumes of my own toward the effort of clearing away the rubble left by that upheaval. But if I were asked today to formulate as concisely as possible the main cause of the ruinous revolution that swallowed up some 60 million of our people, I could not put it more accurately than to repeat: "Men have forgotten God; that's why all this has happened.
Edward E. Ericson, Jr., "Solzhenitsyn – Voice from the Gulag," Eternity, October 1985, pp. 23, 24.
That's not to say that all religions have clean hands, they don't, but humans seem to have an inbuilt need to worship something, and what we worship will heavily influence who we live and act, and how we understand the importance of the lives of those around us. If we don't worship a God for whom all people everywhere are equally loved and important, then we will see others as less than human and do evil things to them (and that can, and does occur with some forms of christian theology). If we worship the state then people who threaten the state must be corrected or killed. If you worship science then people who are "anti-scientific" in your view must be corrected, or if they threaten science, killed. In soviet russia, christians and others threatened the state and its religion of the "science" of Marxism–Leninism, and were controlled, imprisoned and killed in vast numbers.
As has been said before, the only thing worse than what happens when man worships god, is what happens when man worships man.