We are all sinners. Are Hitler's sins any greater than my sins? Is killing 6 million Jews any worse than wishing death to all Wahhabi Mooslems? It only takes one sin to damn us to hell. Isn't His blood and His grace sufficient to cover all sin?
I am not arguing if Hitler was a Christian or not, I am arguing that this is a silly debate for Christians to fall for.
If you can ask that question, you are morally clueless - whatever your religion may be.
Let's just say that I'd much rather have YOU for a neighbor.