The dawn of civilization

[Angrboda]

Kind of moot anyway, as what rulers forced on people was the abandonment of religion as a public act. Like prayer in school, it's hard to ban the private act. But is the banning of religious acts atheism? I think not. These states may have encouraged atheism among the populace, indeed very strongly via re-education camps and indoctrination, but it is notoriously difficult to force anyone to not believe something that they do believe, a fact which has bedeviled competitive zero-sum religions like Christianity for a long time. Ultimately, when you have competitive beliefs, it comes down to a question of the carrot or the stick. I'm not a historian so I can't evaluate the relative uses of both in the named countries and historically in religions generally. What I do know is that the religious, in line with the obligations of their zero-sum game, are attempting to force everybody to believe as they do in so far as they are able. Your ultimate point seems to be that the injection of atheism into society has resulted in mass killings. I might point out that the same can be said about Christianity and Islam, but it's not the point I would focus on. As I raised with tack, the question is not whether atheism is associated with states that have engaged in mass killings, but whether or not atheism is what motivated them to engage in mass killings, and the generally considered answer to that question is no. That's not the same answer we get when we apply the question to religions.