1. Police are not prison guards. But they wear uniforms and have powers.
2. In the Stanford experiment the guards and prisoners are selected at random. Very quickly the guards begin to act outrageously.
3. What happened in Waterford, with Garda giving a beating to that guy, that shows the kind of warped psychological behaviour you see in the Stanford Prison experiment. They were sober professionals dealing with a drunk. What happened should not have happened. Even, people who attempt to make excuses for the garda involved, are falling into the same trap.
4. Police shouldn't use gratuitous and excessive force, ever. You could see it in those protests in New York, where a policeman, who no reason (there's plenty of video to see it from all angles), sprays some girls in the face with pepper spray. He wasn't under threat, there wasn't a disturbance - something must've clicked inside his head.
5. My own experience of being arrested (on the basis I believe of not liking da look ah me). I was made strip to my underwear, I believe for no other purpose just to humiliate me. I was even questioned about a photograph of my ex-girlfriend that was in my wallet. Again, for no other purpose but to humiliate me.
2. Actually at first the prisoners started acting outrageously. The guards had to control this outburst. It was subsequent to this the guards began thinking of ways of controlling the prisoners who outnumbered them and they chose unruly methods. However this was 36 hours into the experiment. It's very rare that police have someone in custody for that lengthy of time.
3. They were trying to deal with a violent and uncooperative drunk for the record and their level of force appeared fine until he was subdued. It was at this point the unthinkable happened. And you're 100% correct in saying it shouldn't have.
4. I'm not aware of the NYPD case at all. I know not of any provocation, indiscipline or otherwise on behalf of police or protester. Police can only use violence if it is legal, proportional and necessary.
5. I know nothing of your case so I cannot comment.