One sentence that throws the problem of evil out of the window.

[Mr.Obvious]

I don't think one has to think God gives specific talks to you to think you are doing his will. I don't think every catholic nazi, every jihadist, every Westboro baptist church hatemonger, every christian klu klux klan member, ... that did horrible things in the name of God thought God spoke to them specifically. Same could have been with Hitler, without it being a sign of what we lable insanity.

For instance, you may not think God speaks to you directly, right? But I'm guessing you do have your notion of what your God expects you to do. Same concept, just far less extreme. You have your own idea of a Godly life and live by it, accordingly. In your case it just might be rather benign
But that's one of the great problems a lot of atheists have with religion. If you believe God is on your side, in agreement with your preconceived notions aqcuired through your social and natural surroundings and your own genetic make-up as wel as your upbringing, anything becomes excuseable. As long as it is in the name of the lord, nothing is truly evil. Including trying to gut your own son atop a mountaintop.

Praise be Him.

I'll ignore the sarcasm, since I am taking the time to answer your questions and have an honest discussion with you. 

Generally speaking if a person genuinely and sincerely believes that what they are doing is morally good, I do think a certain level of culpability is lessened.  

But I find it impossible to believe that going as far as murder and torture of millions of innocent people and children is sincerely seen as morally good by any sane person. I don't believe it. I think many people will rationalize it and tell themselves it's good, or pretend it's good, but I think deep down we all inherently know that mass killing and torturing innocent people is bad, and it takes either a bad or mentally ill person to do it. 

As for Hitler, I don't believe for one second his God claims were genuine: https://en.wikipedia.org/wiki/Religious_...olf_Hitler

Don't ignore the sarcasm. And that's without sarcasm. I just thrive on the stuff. I find that sarcasm can be a decent part of conversation. And I'm not saying that to be contrarian. Often it's just that nothing signifies to my conversational partner better what my feelings on a subject are. Sarcasm isn't dishonesty; it's one of the most honest utterances one can provide.

And all religious books are filled with holy wars and mass extinctions and God-sanctified invasions. Over human history billions have thought that killing in the name of God(s) was good. From the Vikings to witch-hunters in America, from the Crusades to modern Jihad... From Samuel 15:3 to Quran 4:89... Billions have thought numerous crimes that you and I deem horrible and unfathomable in accordance with a (or more) perfect, loving God(s).
I do not label those people insane. Insanity is something else.
Ignorant. Cognitavely dissonant. ... More the terms I'd use.
And yet all of them thought and think they were and are on the right side.

And it doesn't matter whether or not Hitler was a catholic or not. That's why I said it didn't matter earlier, whether or not he believed it: He profiled himself and his vision as such. Many of his followers were catholic and by profiling his movement as such, whether or not he believed it himself, THEY did find a way to justify those horrid actions.