I think the reason why the experiment, if true, is so fascinating is because it's about normal people put into an abnormal situation rather than inherently bad people being given power.
What I take away from the experiment is that given the right situation and pressures, most people would do things they thought they would never otherwise do. More importantly, I think it's probably a mistake to think that you're the exception and are morally incorruptible.
This is exactly the conclusion they want you to reach. Who are you to judge? Who are you to condemn anyone since you are evil too? This is the charter of liberty for evil and all evil needs to survive, even prosper. This "experiment" is the biblical tenet of Original Sin masquerading as science and I reject it. If your moral principles cannot be practiced consistently by all men then something is wrong with your principles, not human nature.
What I take away from the experiment is that given the right situation and pressures, most people would do things they thought they would never otherwise do. More importantly, I think it's probably a mistake to think that you're the exception and are morally incorruptible.