So basically, he was human. A bad one I grant you but human. And that's what causes all the injustice in this world: human behaviour. Remove religion and people will still be good or bad. People will still get slaughtered in the name of dogma; religious, political or whatever.
Another quote from Hitler: 'You are either a Christian or a German, you cannot be both.'
Devout Christian or bad man who said all sorts of scollobs to whatever mattered to his target audience? Make your own mind up.
As someone else said, it most certainly it is a Christian festival and the clues are all there. Just because atheists like yourself pick and choose parts that they like and adopt those doesn't stop it being a religious festival.
And the fact that atheists are happy to perpetuate the tradition...
Presumably you practice atheism at home meaning that you don't celebrate Easter or Christmas. No presents, no Easter eggs or do you pick and choose some aspects to follow? I'm aware that Easter and Christmas are pagan festivals adopted by Christians but you're no more a pagan than a Christian.
I'd argue that it was mainly a racial issue. I'd also argue that atheists killed many, many millions more in the name of socialism in the 20th century alone than the warped minds of religious zealots managed. I'm not sure where all those deaths fit into your 'cornerstone' theory.