They can boot him at the gate, once he’s boarded and in the seat its different criteria.
And just because United wants to give his seat to an employee isn’t in that criteria.
I simply don’t think you are correct.
A business can boot anyone for just about anything and in this case the agreement when one buys a ticket is that any passenger can be bumped.
Doesn’t matter of one has boarded the plane or not.
And, let’s say it did matter, he was off the plane and ran back on without being boarded.
I am not condoning the airline policy or behavior of the airport cops.
I am pointing out another side of it that to my mind is obvious via-a-vis his childlike behavior.
Adults do not throw temper tantrums like a child in the terrible twos, even if being treated unfairly.