He wouldn't have turned away, nothing would have stopped any of them.
The people Hitler chose to serve him were those who would follow him willingly anywhere, even to death. None of them had strong personalities, and they'd rather go kill Paarthurnax after finding out he's against Hitler than anything else.
I have read so many threads in which people have refused to kill Paarthurnax because he expressed remorse and helped those that he once slaughtered with no remorse. Would most people have done the same for Osama Bin Laden, Saddam Hussein, Mussolini, Stalin, etc.
Maybe if there was any more detailed information given than "commited great atrocities against mankind", and hadn't he just waited for thousands of years on top of a mountain to help me save the entire world, the entire universe; yes, in that case I would have killed him.
But none of these disgusting people you name have ever done anything similar. They didn't stand strong for anything, not even their own principles, and even less people trusted them to any higher degree. They served their own whims, and that's it.
Don't know why the fantasy world and real world should be mixed up though. I can only imagine the US and Russia going on a conquer spree to Tamriel after great oil reserves are found and confirmed.