Like others have mentioned… there are good cops and bad cops. Unfortunately, a bad cop has more power than is reasonable in some circumstances. Bad experiences can lead to fear or uneasiness which is understandable and happens to people in all areas of their lives.
I personally have had both great and horrible experiences in relation to law enforcement and law enforcement officers.
I work in the courts and therefore have a close relationship with their occupation as they do mine. I also have friends who are in the police force. However, in the wrong place at the wrong time, I have witnessed behaviour by police officers that I personally feel is unfair, unjustified and inappropriate for their level of power.
Not all police are nasty but it can be incredibly intimidating to be on bad side of one even through no fault of your own or your fault but excessive force is used.
I think it is completely reasonable for various people in all walks of life to feel strongly towards police depending on their life experiences. (Negative or positive).