The Milgram experiment revealed our obedience to authority

In 1961, Yale psychologist Stanley Milgram asked ordinary Americans to administer what they believed were escalating electric shocks to a stranger, simply because a lab-coated authority figure told them to. Sixty-five percent of participants continued to the maximum 450-volt level, despite hearing screams of pain. The study was prompted by the Nuremberg trials and remains one of psychology's most disturbing findings about how far situational pressure can override personal morality.

Source: Milgram, Behavioural Study of Obedience, Journal of Abnormal and Social Psychology (1963)