Psychologist Phil Zimbardo showed that we all have a dark side, one that can emerge quite suddenly, in his famous StanfordPrisonExperiment, which was cut off early when students who played prison guards became sadistic and those who played prisoners became depressed.
They have looked again at the famed Milgram and StanfordPrisonExperiment studies from the 1960s and 1970s, and have come to different conclusions as to why people do the wrong things when they believe an authority wants them to do so.