It has been said that government is force, and for those that doubt this, just look at the power that any given police department has within its community in its ability to confront, interrogate, disrupt, and arrest just about anyone that it so desires, understanding that in virtually all circumstances that these specific police force actions and policies will be back by the powers-to-be. The police force does the things that it does within a community not so much because it is a power unto itself, but more akin to that there is an implied understanding as to what actions that the police may take that are desired or considered desirable by the status quo. This means that while we can rail against injustices performed by police officers within our community, ultimately little or nothing will change, unless those that control those forces, sometimes little known, make it a policy to do so.
While we might like to think that our police force is really here to "protect and to serve" its community, the reality of the situation is, that the police force answers mainly to those that have the money, power, and authority over them, and these influential people may well have a diametrically different viewpoint of what they wish their police force to accomplish within a given community. While it may be true that a notorious case can become a nationwide cause célèbre, as well as it can be true that certain media outlets can focus attention on particular outrageous police actions, for the most part, to effect real long-lasting change within your community in regards to police force actions and its attendant mindset, there must be a change of perspective from those that have the ultimate power over the situation.
This means that if you are not part of the status quo, that if you are not part of the city council, or the city manager, or the county executive, or the city commission, or the mayor, and assuming that any of these positions are the effective manager(s) of the police force, your power as an individual citizen to effect change is virtually negligible. For instance, the one thing that any competent police force is good about doing is following structure, rules, bureaucratic paperwork, and order; which means that the appropriate civil authority which is the administrator to the police force has the power to mold such a force in such a way so as to have the police behave in a way that it is acceptable to community standards.
While it is convenient to lay all of the blame of excessive police brutality, violence, discrimination, unequal application of the law, at the feet of the police officers themselves, in actuality, you would be far better to lay the blame to where it should be, upon the shoulders of the status quo that actively encourage and abet this behavior by police officers within their community. The fact of the matter is, federal law trumps state or city or county law, and all the civil rights that citizens essentially need are contained within the 14th amendment to our Constitution, which states that all persons are entitled to equal protection of the law as well as the due process of law.
If, in fact, the application of law is discriminatory within your community, recognize that the real enemy is often not the police, for these are best seen as messengers of your community law; the actual enemy instead is those that mastermind the police force, becoming a law above Constitutional law.