Just because the police department has diverse management does not mean that the rank-and-file don't have their own issues. Whether it's an issue with training and police academies or a cultural problem endemic in the departments, I've seen and heard far too many things to think that the problems inherent in the current police system (and there are problems) can be fixed purely by hiring black/brown/whatever management. Obviously diversifying the police force helps, but when it comes to arrest situations like the one in question, de-escalation techniques and general empathy are as important, if not more than, racial sensitivity.
I feel that protesting the police (and not rioting) in response is reasonable regardless of where you are, but I don't think it will help much unless something drastic changes either from a federal level or from within police departments.