They're trained to keep the peace. 'Measured', I don't know about. I can imagine they're personally motivated to try and resolve things without resorting to ar

They're trained to keep the peace. 'Measured', I don't know about. I can imagine they're personally motivated to try and resolve things without resorting to arresting someone as that would result in paperwork/processing/etc back in the office. It's not too uncommon to see police get involved in negotiating disputes where there's no specific powers they can exercise (other than removing/arresting the person for trespassing/breaching the peace/failure to obey a 'move on' order). Have the cops turn up makes both sides treat things a bit more seriously - the store manager wants them gone ASAP to stop making a scene, and will be more likely to do whatever it takes to escalate the issue to someone more senior if the police ask.