First of all, it was like 10 in the morning so it seems pretty unreasonable for the officer to immediately jump to the conclusion that there might be a DUI going on. And I take issue with your whole premise that a cop needs to be checking into everything that might possibly be a bit out of the mainstream. Cops shouldn't be involved unless there's actually a concrete problem.
But even accepting your premise, once the cop got up to the window and saw there was nothing going on, he should have walked away. But a mere citizen dared to challenge his authoritah, so he escalated things until they got out of control.
I work on the side as a referee for a pretty high level of sports. So I have authority over the players and coaches that I interact with. But one of the most important parts of my job is being able to DEescalate confrontations, even if it means that the players/coaches get in a few nasty words that I ignore. Cops should be the ones calming things down, but instead, we see too many of these situations (like this one, and the dude sitting on his mom's porch) where they are really the only ones causing the problem.
