These threads usually go the same direction, and I rarely comment. It's often the automatic assumption that the officer has a chip on his shoulder, when it could just as easily be the photographer.
But... Lets paint a different picture.
Officer conducts a nighttime car stop for unknown reason in what is described by a poster here as a not so great part of town in a city with a very high violent crime rate.
Our photography student heads out into the street while the officer is focused on conducting business, possibly anticipating an arrest from the car. Perhaps he startles and blinds the officer with an SB800 flash and some up close paparazzi style photography.
Officer barks at him to knock it off, back off, and get out of the street. Now half blind he is still trying to focus on the occupants of the car, worried about his own safety, the safety of the photographer, and the occupants of the car. But, maybe our photography student backs off a few feet and continues to flash him while mouthing about his right to do as he pleases in public whilst paying his salary.
Distracted and unable to conduct the business of the car stop and possible arrest safely, the officer again sternly rebukes the student tells him to knock it off, orders him out of the street, and tells him he is likely to end up in jail.
Perhaps our student takes his sweet time doing so, mouthing and flashing away the whole time, and ends up on the sidewalk on the other side of the car. From there he continues to flash the car, the officer and is running his mouth the whole time. Perhaps the car stop situation is escalating to an arrest or relatively dangerous situation while all this transpires.
OK, car stop business completed, the officer goes over and tells the student that he is under arrest and places hands on him. Student bucks up, tries pulling away and gets put on the pavement for his efforts. Girlfriend runs up starts pulling at the boyfriend/camera/officers and finds herself arrested for her efforts.
So did it happen that way? I have no idea. But, it's just as plausible and more likely to me than the general assumption that the police are thugs and college students always make good decisions. Just saying... Could it be that the officer was just a jerk? Yes, I acknowledge that as well. I just don't assume it.
Someone here pointed out that "For street photography and other activities, it's vital to increase one's situational appraisal skills.". Social and situational appraisal skills are often not a college students strong suit but I think that it is an applicable element in many of these situations.