Yes, police are there to enforce laws, but I would argue to differ on that they are there to protect you. They are there to protect society in general, not necessarily you, and the powers they have only allow them to really put you in jail (or taz you and put you in jail, or shoot you and put you in jail, or shoot you and put you in a grave). That is really the extent of their power.
If you don't believe me, go read the miranda rights. By talking and interacting with police, they only thing they can really do is put you in jail. It is not up to them to prove your innocence in a potential crime, they are there to prove you guilty, and anything you say or do can and will be used against you.
I'm not saying this is a good thing, but it is the current reality that we live under. 50-70 years ago, this simply wasn't the case everywhere in the nation, but not anymore (sure there were sections, especially if you were a minority that this happened to even back then). You can't simply talk to police anymore, because you don't know the laws, and you don't know what other testimony that the police may have already been given before they come to talk to you. And since they don't have to tell you the truth, you can not even believe anything the police tell you, because it could simply be a tactic to get you to be arrested.