Some theists argue that atheism was responsible for the deaths of so many people at the hands of Hitler, Stalin, Pol Pot, and Mao.
The claimants fail to realize that these individuals simply happened to be atheists (or were they?) who had ridiculous ideas that lead to the deaths of millions. There is no logical connection from "I don't accept the claims of theists" to "I'm going to set up a personality cult, brainwash a nation, kill people, and take over the world."
If a high-school student was very interested in Greek mythology and killed students at his school, would you blame Greek mythology? The reporters found dozens of books in his house! It must have been that belief in Zeus!
The idea that Hitler was an atheist is actually very questionable.
The Nazi regime forced the German soldiers to wear religious symbols such as the swastika and they placed religious sayings on military gear. An example here is the German army belt buckle which reads “Gott Mit Uns”. For those of you who do not speak German it is translated as “God With Us”.
“We were convinced that the people needs and requires this faith. We have therefore undertaken the fight against the atheistic movement, and that not merely with a few theoretical declarations: we have stamped it out.” -Adolf Hitler, in a speech in Berlin on 24 Oct. 1933
"My feelings as a Christian points me to my Lord and Savior as a fighter. It points me to the man who once in loneliness, surrounded by a few followers, recognized these Jews for what they were and summoned men to fight against them and who, God’s truth! was greatest not as a sufferer but as a fighter. In boundless love as a Christian and as a man I read through the passage which tells us how the Lord at last rose in His might and seized the scourge to drive out of the Temple the brood of vipers and adders. How terrific was His fight for the world against the Jewish poison. To-day, after two thousand years, with deepest emotion I recognize more profoundly than ever before the fact that it was for this that He had to shed His blood upon the Cross. As a Christian I have no duty to allow my self to be cheated, but I have the duty to be a fighter for truth and justice… And if there is anything which could demonstrate that we are acting rightly it is the distress that daily grows . For as a Christian I have also a duty to my own people." –Adolf Hitler, in a speech on 12 April 1922
"The personification of the devil as the symbol of all evil assumes the living shape of the Jew." -Adolf Hitler Mein Kampf
“The best characterization is provided by the product of this religious education, the Jew himself. His life is only of this world, and his spirit is inwardly as alien to true Christianity as his nature two thousand years previous was to the great founder of the new doctrine. Of course, the latter made no secret of his attitude toward the Jewish people, and when necessary he even took the whip to drive from the temple of the Lord this adversary of all humanity, who then as always saw in religion nothing but an instrument for his business existence. In return, Christ was nailed to the cross, while our present- day party Christians debase themselves to begging for Jewish votes at elections and later try to arrange political swindles with atheistic Jewish parties-- and this against their own nation.”–Adolf Hitler (Mein Kampf)
“Hence today I believe that I am acting in accordance with the will of the Almighty Creator: by defending myself against the Jew, I am fighting for the work of the Lord.” –Adolf Hitler (Mein Kampf)
So, even if Hitler were an atheist, would you expect a speech like this to be the cause of his evil?