” .......as they two argued over the law.”
That is where the cop made his first mistake. He did not write the law, his job is to enforce the law. Enforce the laws as written by elected representives of the people. Laws are to be argued in court or in city, county, state or national legislatures.
He should ask himself, “How would Deputy Frank handle this?”
https://www.youtube.com/watch?v=_fOd6d0Z9RA
Cops werent really arguing. He told the dude to get out after it was clear he wasnt going cooperate with the law. They were going to pull him out. The victim chose poorly.