Most likely, Hitler was a kindly man to his maid.
I think we want to think of Hitler as an undifferentiated bundle of psychotic rage, with no normal human emotions at all, because we want to distance ourselves from our own capacity for evil. Most of us are capable of monstrous acts, even if we'd never go as far as Hitler did.
I've known otherwise kind people say -- and mean -- some really monstrous things. "We ought to send all the ******s back to Africa." "We ought to bomb Iran back to the Stone Age." "The government has to use torture." "If he wasn't guilty, they wouldn't have arrested him."
If we don't admit Hitler's humanity, we don't have to face our species' potential for unspeakable evil. We can say, "Hitler killed eleven million people," and we don't have to think about the millions who carried out his orders -- the fathers and mothers and fresh-faced young people who did the actual killing, the clergy who went along, the young girls who had crushes on Hitler, the masses who thought he was a defender of their people
We want to believe that Hitler was nothing like us, but it's not true. People like Hitler and Stalin and Pol Pot and Idi Amin and Tamerlane and Mao keep popping up in our history. Admitting we've got a problem is the first step.