tenyearsafter,
While your anecdotes are apreciated; the issue with police anecdotes are that precincts and districts vary so ridiculously widely across the country that the only dualities between them may be the most core facets of the job.
Police in Baltimore were literally trained to beat up kids standing on the corner idling, or beat up suspects in the back of the cars that got "too lippy" with them, because they were trained that their Districts were basically war zones, where the only way to keep those people in check were with threats of more violence. Police on Coronado Island, San Diego basically hand out a few traffic tickets or handle a domestic dispute from time to time. In a mixed area like I grew up in (where city lines shift poverty lines greatly), you see almost the entire range of officer. What an officer in Bloomfield Hills has to deal with is hugely different than one in Warren, which is just 15 miles away.
What is being asked for IS for more of the "bad" police, or bad policies, like were enacted in Baltimore, to be filtered out. A person's personal safety should never be left to the whim of if someone in authority was having a "bad day" that day or not if possible, and there should never be "beat them up when no-one is looking" policies in place for ANY departments. And do away with that whole "code of silence" thing where officers stick up for and cover for each other no matter what as well. That's the kind of stuff that people are trying to change, and those things CAN be changed from an institutional level.
You can't make poor desperate people not do bad things as a whole, because that's human nature, but you CAN try to fix things on an insitutional level so that there aren't so many poor, desperate people. Similarly, some power hungry jerks will always try to gravitate towards positions of authority, such as police, but you can attempt to make it harder for those types of people to run around unchecked once they're there. That's what the main focus really is.