Dr. Stanley Milgram:

"The results as I observed them in the laboratory are disturbing. They raise the possibility that human nature cannot be counted on to insulate men from brutality and inhumane treatment at the direction of malevolent authority. A substantial proportion of people do what they are told to do, irrespective of the content of the act and without limitations of conscience; so long as they perceive that the command comes from a legitimate authority. If in this study, an anonymous experimenter could successfully command adults to subdue a 50 year old man and force on him painful electric shocks against his protests, one can only wonder what government, with its vastly greater authority and prestige, can command of its subjects."

--Please keep in mind, 65% of the participants in this experiment continued until the end despite the fact they faced no physical threat for refusing their "orders." How much worse might it have been if they knew "refusal" would be met with punishment? (Perhaps some electric shocks of their own, or worse...)

For more information on the Milgram experiment, and follow up experiments, click here.