Or, as HAL said, and the direction robav8r was going, the Captain simply says, "I am not taking the aircraft with that guy on board because he is a disturbance and has refused to obey my cabin crew". Flight canceled, everybody hates the Doc as they deplane. Once in the gate area, security nabs the guy and they re-board. Hind sight is 20/20 though.One way United could of handled it: Declare the plane broken, de-plane everyone, then declare plane fixed. Re-board minus the selected (security at the gate). It would cost time, but it certainly wouldn't be in the national news.
On legislating no over booking, I can dig it. You guys pay more for a ticket so I can ask for a raise. The hitherto fore full planes now have empty seats for Mrs. Wink and me to fly off to exotic destinations free of charge. Thanks Congress. You go!!