Of course they are. We are now at the point that when a black man attacks a cop and gets shot it's automatically a racist cop that did it, and we'll see protests. This default conclusion is itself profoundly racist and excuses the instigating behavior.
No, what you are seeing is that cops, as a profession, have lost our trust. It is not something that has happened in the last few years, but has been on the decline for decades. They got a temporary boost due to the individual heroism displayed around the events of 9/11, but that boost has worn off now, and it makes the ugly racist norm of police work even less palatable by comparison.
Although police brutality is a real thing and they don't in general treat blacks as well as non-blacks, the golden rule remains stop attacking cops, stop getting killed by them. No protest is going to encourage a cop to stop defending themselves when attacked. Lost in the marching asking why these unarmed black teens are getting killed is the question why are they attacking people? Cops will quite happily shoot to death anybody who attacks them of any race and we all know it.
We will soon have to do something about this problem as more and more people are starting to see police not as a civil servant that will help and protect them, but as a potential threat to be feared. It is the police that will have to change, they will have to give up some of their authority, add more transparency, and hold each other accountable for every breach of the law. They will have to hold themselves as shining examples of lawfulness if they wish to be the enforcers of the law. Fail that and these protests will soon turn to mobs, and those mobs will quickly learn to turn their anger against the people that they fear. We have already seen the start of this, we need to take action now to hold off anarchy.
The most infuriating thing about this is just how many fuckers are totally cool earning their living off of making people suffer like this. "Fuck all those human beings, fuck their freedom, fuck their future, fuck their families, as long as I can get a nice paycheck and a fat pension." THOSE asshole cops/lawyers/prison-guards/judges/wardens are the ones that should be in jail for the betterment of society.
The problem is that these people are constantly told that they are heros. They are patted on the back by society and told that they are protecting us. It is easy to delude yourself when you are constantly being told that you are doing good. It is easy to be cruel when the people you are being cruel to are defined as OTHER.
We need an entire paradigm change in our justice system. We need to stop seeing crime as a individual failure and see it instead as a societal failure. We need to stop worrying about punishing individuals for crime and instead seek to heal criminal behavior as an illness.
We need to recognise that our anger will not fix the problem but maybe our compassion can.