I'm not sure if Hitler claimed to be Christian, but in any case he was not being a Christian when he was doing the things he is infamous for.
Just for the record, I’m not an atheist, but an extremely skeptical agnostic. If you didn’t know that, and observed my life, you would likely assume that I was a very devout Christian.
In that case you are closer to being a Christ-follower then those implementing the Spanish Inquisition. Being that the way you live your life is more in accordance with the teachings and examples of Christ. Those torturing the Jews may have been convinced they were following Christ, but I believe it when Jesus warned that there would be those that called Him "Lord, Lord" and yet be damned on the day of judgment when He will tell them "I never knew you". And there are many examples of Jesus being harsh on the religious hypocrites of His day. The term "brood of vipers" being used more then once.
http://www.davnet.org/kevin/essays/hitler.html