There was a very complex and interesting programme on PBS America called 'Radical Evil' about the Nazi death squads, who gunned down about 2 million Jews. These were young men ordered to shoot large groups of helpless men, women and children, over and over again. The programme asked how this could happen, that ordinary young men could do such a thing. They committed mass murder but were they responsible when you consider the complexity of the offence? They could not refuse the orders, they were brain washed into believing it was the right thing to do, and the human brain learns how to adapt into acceptance of what is required when it has no choice. Very complex issue.