That’s a private dispute, that’s not the same as what happened here.
Here you have a law enforcement officer, with all the special tools and powers given by the State, punching a young, helpless woman and apparently arresting someone for saying one sentence, in a country where there’s Constitutional protections on free speech.
So, what law can you break by saying one sentence? Yes we don’t have all the details, but from what we DO have on video, this looks real bad for the cops.
From what little we do know, it was apparent that we had an underage young woman in possession of alcohol on the beach and the cops were initially willing to let her go after determining she wasn't intoxicated. But instead of counting her blessing and getting on with her weekend, she felt compelled to be disrespectful to the cops. Yes, her free speech rights and all. But it is always unwise to be a smart ass with cops, especially when they just cut you a break.
Ironically, if the young woman went on her way, got drunk, and then had a DUI incident later that day, those same cops that cut her a break could be held legally responsible. We would all be attacking the cops for letting an underage drinker just walk away.