It’s interesting to compare this in the light of @David_Spardo 's comments about the truckers forum discussion:
My feeling is that if you can put the ‘problem people’ into a category that ‘must be dealt with, regardless of cost’ and tell yourself that they deserve it then you can do almost anything to a stranger. It can be very hard to overcome those feelings that ‘these people’ don’t matter and and to recognise they have a value too when that goes against ones culture and peers. This seems to be normal human behaviour, based on how quite different races deal with those they don’t want in roughly similar ways.