Because we, the police, and everyone else confuse the ideas of the Justice System and the Legal System.

One is an ideal to try to create equality in society and the other is to maintain a system of power and control.

It makes you wonder and look at the history of why we have police in the first place. They aren't there to serve or protect people, they are there to enforce laws which were prominently created to protect wealth and property.

Even the term 'to protect and to serve' is a marketing term created by the Los Angeles police in the 60s to deal with a terrible image they had at the time of normalized police brutality back then.

The oath that new police officers take is even suspect, in my province in Ontario in Canada where this is used:

I solemnly swear (affirm) that I will be loyal to Canada, and that I will uphold the Constitution of Canada and that I will, to the best of my ability, preserve the peace, prevent offences and discharge my other duties as (insert name of office) faithfully, impartially and according to law.

The statement doesn't say how they will perform these duties..... it can just as easily be used to justify the use of force at a protest against an unpopular government, business or corporation. It also just states that they are meant to uphold laws, it doesn't say they'll be nice about it.

It gives you a perspective on the image that they are just LAW ENFORCEMENT, not necessarily a group that is meant to be nice to people, especially when those people disagree with society or the government.