I think policing in America is facing such turmoil that these issues may never be solved in ways that will satisfy society.  For one thing, modern policing roles are like a mix of a number of personalities all rolled into one, with no one being able to exactly define what the pre-dominate role of a police officer actually should be.  Then, you toss in the individual officer and his or her own definition of his or her role - is the officer a law enforcer, social worker, first aid provider, community problem solver, an intermediary between disputes, a revenue collecter (tickets, et cetera), a crime fighter, a crime solver, and on and on.  Sort of a jack of all trades, master of none - the problem only increases. 

Oddly, that is one of the great things about policing - there are so many roles one can fall into (sadly, too many officers want to be one type of cop when they are actually better suited for another type).

For myself, I knew my greatest skills and interests were of that of crime scene investigation.  I knew from the get-go that my skill set was not that of a drug cop or traffic cop (man, I HATED writing tickets and ANYONE could talk me out of one very easily - I once caught holy hell from a prick of a supervisor because when confronted over my dismal number of tickets per month I told him I thought ticket fines were too high. He promptly suggested I find another line of work).  After doing what I was meant to for seventeen years, somehow I ran afoul of our current chief at the time and he decided I needed some time back in patrol (I never did learn what it was I did other than I was not a favored son of this man that surrounded himself with many "loyal subordinates" and demanded they bend at the knee).

You are so right about initial impressions on so many calls - by both police and those responded to.  One time I was dispatched on a call of a large group of "suspicious" black males sitting on a porch of a house that they were not supposed to be around.  As soon as I got out of the car the males declared I was there because they were black instead of letting me explain to them that I was just there because I had been sent there (it turned out that one of the youths was a grandson to the homeowner but that the grandma did not want him around when she was not home).

I did hear the "because I'm black" many, many times, but I imagine through experiences that that was a warranted belief (One time I stopped this truck at night and without even knowing the race of the people inside.  The driver was a young white male from a nearby town known for its tremendous racial animosity toward blacks.  His girlfriend was a young black girl and the first words out of his mouth that night was, "You stopped me because I'm white.").

One time when a rookie, I backed up a fellow officer on a car stop, and inside the car was four or five young black males.  After the car stop was over, I asked the officer what the driver had done and his reply was, "you know someone is dirty when you have a car full of 'moolies' inside."  I can honestly say I never conducted traffic stops like that. For one thing, it just isn't right and more importantly, for me, I would use my behavior with people to build credibility that I was a fair cop and for them to ask around if they doubted it (hell, there was this sort of running joke I had with this one young black male because time and time again he would park in the worse places to avoid the police to toke up.  He really was a good kid but just liked his weed.  Each time I would chastise him and suggest he find a better place to spark it up.  I never did take enforcement action against him). 

Police departments really need to explore better hiring practices, though sadly, the recruitment pool is getting smaller in both size and depth.  When I was hired, the hiring process was this battery of tests more or less conducted to weed out the type of person employers DON'T want to hire.  Studies have shown that tests that do this are not always the best ways to find police candidates.  Studies have also shown that a better selection process involves really learning more about a person's internal character and this may be more beneficial in the long run (supposedly because a person's personal integrity remains consistent through one's life). 

Now here is a sad thing about where I'm located - a couple of years before I retired, people within personnel of our municipality went to the local head of the NAACP and begged for help in recruiting minority officers and was turned away. 

And don't get me wrong - I feel such an internal turmoil to what is going on, especially when it comes to the gray areas and of incidents where the benefit of the doubt should remain with the officer, but at the same time, these really horrific and clear incidents are so very, very troubling.  And it does not help how these incidents do piss away any goodwill the good police have built up over the years.

Best wishes, don't know if I answered adequately or not...