In “Obedience to Authority: An Experimental View” Stanley Milgram writes:

“Obedience, because of its very ubiquitousness, is easily overlooked as a subject of inquiry in social psychology. But without an appreciation of its role in shaping human action, a wide range of significant behavior cannot be understood. For an act carried out under command is, psychologically, of a profoundly different character than action which is spontaneous.The person who, with inner conviction, loathes stealing, killing, and assault may find himself performing these acts with relative ease when commanded by authority. Behavior that is unthinkable in an individual who is acting on his own may be executed without hesitation when carried out under orders.