The passenger was in the wrong. That does not mean he wasn't wronged. All three parties here are wrong, some more than others.

UA screwed up, and was incredibly greedy. In this situation, where you are bumping pax for crew (even though it was the right thing to do), you need to continually increase your compensation until it becomes an easy decision for four people to comply. If you get to $1k-1500, sure as daylight you're getting people off that flight happily.

After UA's greed, the passenger that was selected to be removed needed to do so. This is not a choice. UA has the legal right to remove him- whether or not that is fair. He was asked to leave, he refused law enforcement. He was wrong.

Law enforcement certainly seems like they used uneccessary force. We don't see the whole thing. How many times did they warn him? Did they inform him that they were going to forcibly remove him if he did not comply immediately? If they warned him several times and also warned him he was about to be forcibly removed, they did no wrong. That's a tight spot to be gentle- it's almost impossible. That being said, if they escalated to force quickly....they were in the wrong.

UA should be ashamed of itself for not being aggressive enough in compensation and allowing corporate greed to result in this incident. The passenger should learn that, whether or not something is fair, it is NOT ok to refuse to listen to law enforcement. Then we have anarchy.