It wasn't a properly controlled experiment to begin with, nor was it repeated. General conclusions should not be drawn from a single, flawed study. But it makes for good headlines and talking points.
And some people really WANT to believe it's true. They've built their entire worldview around it and the idea they've been duped would cause a massive narcissistic injury.
https://en.wikipedia.org/wiki/Milgram_experiment#Replication...