"The only difference between them was a coin flip"- HIGHLY DUBIOUS claim
The so-called scientist in this film makes the assertion, "The only difference between them [a guard research subject and a prisoner research subject] was a coin flip." That claim is highly dubious. Yet it is meant to infuse his thesis with scientific legitimacy and prove it as true.
Basically, this film is presenting that highly dubious claim as a "scientific fact," in order in turn to assert the idea that science proves all people assigned to guard duties in a prison would behave like psychopaths.
Those assertions are so absurd I don't even know where to begin with debunking them, because they could be debunked in legions of ways.
I.e:
How did the researchers determine that their subjects were exactly the same, apart from a coin flip? By interviewing each subject for an hour or two? How could that possibly be enough time to prove that two persons are identical?
How do the researchers know that the subjects were honest in their screening interviews? In fact, the film itself shows the research subjects flubbing and fabricating some of their answers, which indicates that they were not entirely honest. In this way, the film itself contributes to debunking its own core "scientific fact"/"moral lesson!" LOL
How could two people even possibly be identical apart from a coin flip? They have different genes, they have different spirits, they have different brains, they have a countless number of different life experiences, etc. Heck, even identical twins with the same genes who are raised in the same households are not exactly the same in every way. That fact alone pretty much renders this film's assertion that two non-identical, unrelated people from different households could be exactly the same apart from a coin flip as sheer bunkum.
How do they know that the two research subjects who they were analyzing are equivalent to any and all other human beings?
How do they account for all the real prison guards who disprove their thesis by not behaving like psychopaths?
In summary, this film's core assertion is highly dubious, and based on flaky "science" that does not hold up to any form of basic scrutiny.