Aah, that must make it acceptable then.
Try telling that to the millions of Jews he had exterminated at concentration camps , Hitler wasn't an evil bloke you've got to take into account he had a troubled childhood " ffs. It must have been down to
a medical condition. History is full of people who were simply born evil. Remember Doctor Harold Shipman who killed all those pensioners ? What would be his excuse, another problem upbringing ?
If its a medical condition how do you spot it and treat it to stop somebody turning into a serial killer 
Depends how "Evil" is defined, I agree what he did or got others to do were indeed evil acts however i've seen programs which suggest that Hitler himself had some forms of mental illness
As you say, saying someone had a hard childhood in itself doesn't automatically lead to them doing bad things. plenty of people had / have hard childhoods but go on to be decent people however they are more likely to do bad things to others than someone who had a good upbringing.
In truth I think it's always a varying degree of Nature Vs Nurture and you do see examples where 3 kids are all brought up the same, 2 do well in life and the 3rd is a total piece of scum yet had the same opportunities as the other 2.
I remember seeing a WW2 program about psychiatrists who studied the Nazi leaders after the end of the war, one of them Douglas Kelley was shocked that in his assessment he had to conclude that the likes of Hitlers henchmen weren't actually mad or evil but ordinary sane people who had ended up doing despicable things to further their own ends
Kelley ended up committing suicide as a result according to his family as he simply couldn't come to terms with how a normal person could sink as low to do the things that they had done
I've always said that the nice societal norms we enjoy in the good times are merely a thin veneer, scratch it and there is something nasty waiting just under the surface

From the link -
The psychiatrist had developed his own pet project — a search for psychological traits common to the prisoners that would allow Kelley to describe a “Nazi personality.” Kelley found something much different from what he had hoped, although he built an extremely close relationship with Göring.
Kelley’s inability to identify the expected qualities of a Nazi mind rattled him, as did Göring’s suicide in October 1946. By that time, Kelley had changed his professional focus from psychiatry to criminology, and he began a long spiral downward through alcoholism, marital strife, workaholism, and fierce inner rage. He committed suicide on New Year’s Day 1958 by swallowing cyanide, the same poison Göring had used to end his life.
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