If a serious crime has already happened, i.e. stolen car, burglary, rape, murder, i guess cops would be useful. They have the needed resources to investigate such things. To call them to diffuse or mediate a situation, well they are often going to criminalize whoever isn't complying with their demands. Or favor whoever appears more respectable and spins a better story. Screw that.
RE: Notifying the police don't do anything anymore.