The airing of Darwin's Deadly Legacy has reignited debate over Hitler's religious views. Of course, public pro-Christian pronouncements by Hitler are well-documented. However, I found out through a recent post at Christian CADRE that CADRE's got a page dedicated to refuting this "This guilt-by-association argument." Funny way to lable it, because the only time I've heard anyone say that Hilter was a Christian is when an atheist or agnostic is responding to the "atheism caused the Holocaust" arguments. A recommended link from that page is Christian, Atheist, or Neither?, which notes that Hitler's public statements aren't necessarily in accord with his private beliefs as found in collections such as Table Talk. Then again, we have Steven Carr using Table Talk to show that Hitler wasn't exactly a fan of the modern scientific worldview.
It's even more complicated than that, though. In an article in German Studies Review, Richard Carrier has noted serious discrepencies among various editions of Table Talk. (See Wikipedia and Carrier's publication lists. Carrier's article is recommended for those who have access to German Studies.) In particular, many main anti-Christian quotes in Table Talk seemed to have been added by a neo-Nazi who put together one edition. Furthermore, all editions contain a quote claiming that Jesus was an Aryan whose techings were abused by the Jew Paul in the service of "proto-bolshevism."
What can we conclude from this? Hitler seems to have had a bizzare mix of beliefs not in accord with orthodox Christianity, but which nonetheless affirmed the existence of God and the authority of Jesus. Neither atheism or Christianity provided direct support for his actions.
Whenever the "atheism caused the Holocaust" line comes up, it's worth pointing out that Hitler was no atheist. However, I wouldn't worry about that too much. It would be sufficient to say, "So what? Aquinas, Luther, and Calvin were Christians." Actually, it would be enough to say, "The Bible was written by Christians and Jews," as the Bible endoreses the full slate of Nazi crimes: killing dissidents, killing homosexuals, and genocide.