If I understand correctly, United Airlines boarded passengers ont a plane for a flight, and then after the fact decided they were overbooked because some UA employees wanted to hitch a ride too. SOP is to deal with overbooking in the terminal before boarding. Since people were already seated, they offered to buy out passengers with cash, a ticked for another flight, and a hotel room. There were no takers after they raised the cash offer. So they randomly picked 4 passengers to kick. One of those passengers was a doctor who objected to being kicked out of his seat, and the airline called the cops to beat him up and drag him off by force instead of trying to make a better deal.

UA screwed up, and they punished a customer.