To people from outside the US, please understand that our police do not go around shooting and handcuffing people all the time. I have never personally known anyone that was wrongfully arrested or abused by the police.
Even in a traffic stop, the key is to be polite and treat the police like human beings. They are understandably concered with each public contact-- American police are killed in the line of duty, sometimes with no warning.
The problem is a political one, and it must be stopped. It' a wedge issue used to divide the voting public, and media sources play to both sides.
If you travel to the US, please do not fear violence from the police. They really are here to 'Protect and Serve'.