Well yes and no. You can say that it’s just the people in any experiment but past a certain point you have to be able to extrapolate the results to the population at large. And (again, if memory serves) the results of this experiment have been replicated numerous times across numerous population samples.
Also, the point of Milgram isn’t that people are fucked up, it’s that people will follow orders when those orders are issued by someone in a perceived position of authority. And it’s funny you mention Nazis because the experiment was Milgram’s response to the “I was just following orders” defence from the Nuremberg trials.
In conclusion: non-fucked-up people will do fucked up things if their boss tells them to.