ChooseDoubt seems to think so.
That cracks me up. The guy goes to church and all of a sudden he's giving full assent to Christ's substitutionary atonement for his sins and a promise to repent of murder and stuff. ChooseDoubt is accusing Hitler of being not just a genocidal madman, not just a freak, not just pretty much the most worthily vilified person the world has ever known, but also a hypocrite! That's just piling on.
So, I have proposed this as a synthesis of what he's presented and the significant amount of conflicting facts out there:
Hitler was a madman who was heavily into a sort-of self-theistic mythological megalomania.
So maybe it's not a great idea to call him an atheist, I can see that maybe. It's worth a different discussion.
But just b/c Hitler appeared in churches doesn't make him a Christian. That's pretty silly. I myself have been known to frequent coffeehouses. That doesn't make me a French skeptic. It means I like what the coffeehouse provides - good coffee. Similarly, Hitler liked what going to church provided - psychological power over a religious populace.