There are some folks who are pretty dead set on maligning Milgram alongside Zimbardo. Namely, Gina Perry wrote a book criticizing Milgram and his experiment's validity [1]. I haven't read it, but looking at some of the reviews, it seems most likely that it's a mixture of truth and the typical schlocky scientific journalism I've come to know and revile. [2]

[1] https://www.amazon.com/Behind-Shock-Machine-psychology-exper...

[2] Funny anecdote- when I was still in science (brain imaging) a reporter from a major news outlet interviewed another member of my lab about what brain activity would look like in a dead person's brain. The question was entirely serious.