Which video did you see? I saw the video where law enforcement personnel physically removed Dao after he resisted their orders. Dao is an arrogant and stupid man, who must think being a medical doctor makes him superior to law enforcement jocks.
I am simply pointing out the difference between police officers and people who are not allowed to carry guns or make arrests, and who behave like thugs.
For all your deference to law and order, you certainly seem to get a weird thrill out of United breaking the law wholesale in their treatment of Dao.