Well, I guess you havent seen the picture from belgian Congo, when they chopped the hands of small daughter of a farm worker and brought them to him to motivate him to work harder.

People can be vicious animals rather easily, once 'the others' are dehumanized its not worse than behavior towards animals in slaughterhouse. it doesnt take much, look at various conflicts around the world, look at how drug cartels in south/central america behave.