Basically, this wasn't just poor customer service, it was a violation of rules.
Basically, this wasn't just poor customer service, it was a violation of rules.
But the fact that United got to that point is the problem. They had the option to offer more money for volunteers, they even had the option to find a different flight for their employees, or maybe send them on a cab ride instead (one passenger in the video even pointed this out while it was happening). Of course, the excessive use of force is on the police and they should be the ones outside of the law on this one, I don't believe being loud in that situation warrants you get a concussion, that's just wrong.
Some people argue that "boarding" continues until the plane is in the air and that the airline can execute their right to involuntarily "denying boarding" to any passenger up to that point. Others argue that the plain meaning of the word means that once you are "aboard" the aircraft, you can no longer (legally) deny someone boarding. They argue that since the contract of carriage does not define "boarding", it must be construed to have the plain language meaning (as in the United CEO in his statement saying that "the flight was fully boarded".)
Airlines may do it all the time but, as far as I can tell, a court has never ruled on when "denying boarding" ends and "removal from aircraft" starts. Maybe now we will find out.