The part of this myth that really sticks in my craw is the fact that it’s always stated as if it means something. Look: If, at the cusp of the Year of Our Lord/Flying Spaghetti Monster 2014, you haven’t realized that religious people and atheists both have pretty good odds of being huge assholes, you are beyond my feeble capacity to educate.
Also, in the interests of baring my biases: I am a Christian.
But here goes anyway:
Hitler was not Christian. In fact, Hitler’s regime was very anti-Christian. His government persecuted the Catholic clergy and attempted to purge the Protestant church in Germany of “Jewish influence,” which is pretty difficult what with the whole Abrahamic faith-angle. The Nazis even went so far as to found their own version of the church, calling it “Positive Christianity,” which removed all those pesky Jews (Read: Jesus + almost all of the Old Testament) and the Apostle’s Creed, and replaced it with Nazi philosophy.
I know the internet is fond of crowing about the “No True Scotsman” fallacy, but when you take out the Apostle’s Creed, what you have (no matter how loudly you call it Christianity) is not Christian.
Hitler was not (in all likelihood) an atheist. Hitler’s views on the existence of God are tough to nail down. He was a secretive guy, and had a mercurial streak a mile wide. He frequently discussed the idea that Germany was created by God, or gods, and that the nation was favored by God. At the same time he frequently derided faith (in anything other than Nazism or himself) as being idiocy.
In summation, Hitler’s religious views were ambiguous, and the question of Hitler’s faith is of dubious value.