It's best to be reasonable when asserting your authority.
John is a police officer who catches some kids loitering on the sidewalk by the corner store.
John wants to let the kids know loitering is illegal.
John tells the kids calmly that loitering is illegal and that it's a law so that people feel safe to walk in certain areas and that they should go home.
John slams down his nightstick onto the concrete pavement making a loud bang as he proclaims loudly that he'll have them all arrested if they don't disperse immediately.
The kids are happy that John gave them a reason behind his actions and was so polite in asking them to leave.
The kids are terrified of John and think he's a maniac and also start to learn that police cannot be trusted or respected.