They may not have to explain, but they should explain. Given the news of the last few months I would have though he would have bent over backward to explain rather than accuse her of “seeming like she was mad...” She said why she was mad. She moved over to be polite and then got a ticket. But she accepted it. Why did he order her out of the car? Was it just because of the cigarette? That is stupid. She did not understand why being unhappy about a ticket escalated into an arrest. I don’t understand either. That cop was a great big jerk and should find another form of employment.
Once you go done that road of “explaining”, it never stops.
You may get a lousy cop. Do what he says. Sign the ticket, drive off free. ‘’Then throw the book at him.
He is in control until you can leave.