What the non-Americans here need to realize is the American culture of policing is very different from the rest of us. The hero complex is alive and well, there has been a lengthy cultural and legal presumption that police are always justified and tell the truth, that policing routinely needs to involve violence, and that the police are rarely held accountable even when there is considerable evidence they've done the wrong thing.
I've worked in LE for years. It is my belief that body cameras are unquestionably a good thing. While I understand some of the apprehension, I don't think police using caution to determine where and when physical intervention is required (as opposed to leaping in and shooting 12-year olds dead:
http://www.cnn.com/2015/10/10/us/tamir-rice-shooting-reports/) and thinking things through is a bad thing.
As it happens, I've even noticed a shift in our use of force refreshers, where there is considerable emphasis on thinking through situations and focusing on the "is this really something requiring my intervention right now." It's a good shift.