What Stanley Milgram concluded based on his famous study of obedience is that people will do whatever they are told as long as they believe that whoever is telling them what to do has the right to order them. They will obey orders from what they think is legitimate authority even if they are ordered to do terrible things.
Milgram reached this conclusion because of how many of his test subjects were willing to continue to press the button even when they thought that, by doing so, they were hurting another person. The study found that 65% of the subjects were willing to continue to "shock" the person at the highest possible level. The subjects did this even though they sometimes felt that it was wrong.
Because of this, Milgram concluded that people in general (or at least members of his test group) are all too likely to follow immoral orders as long as they think the people ordering them are legitimate authority figures.