SPE was fraud, he told the guards to act like "tough guards" and then said publicly “the guards were given no specific instruction or training on how to be guards," which is what made it probably the most famous psychology study of all time.
As if real prison guards in oppressive regimes spend a lot of time in ethics classes.
The idea behind SPE was not to ask if something could happen or how it should happen, but to ask how something did happen. It achieved the results it was intended to achieve, as did the similarly-"discredited" work by Milgram.
The conclusion in both cases was inescapable: if you order someone to commit an atrocity and they refuse, all you have to do is to ask the next person in line. You won't have to go very far or wait very long.
https://gen.medium.com/the-lifespan-of-a-lie-d869212b1f62
https://www.vox.com/science-and-health/2018/6/14/17464516/st...