The CEO of United, Dao’s fellow passengrrs, and video all say/show he was non-belligerent.
Again:
the simple act of refusing to leave IS belligerent.
When your kid lays on the floor refusing to move is that belligerent? Of course it is. When college students stage a sit in are they being belligerent? Again, of course. It is quarrelsome, antagonistic, and contentious, behavior. Period. You don’t have to be making noise or being physical, the direct act of refusing to comply IS belligerent.