Legally the passenger may well have been obliged to leave when demanded. Morally that law is clearly wrong, he had a ticket, he was entitled to stay, and the law ought to reflect that. Why should he be in a position where he is forced to leave to take it up afterwards when it was all fait accompli and a waste of his time and breath ? They need to sort out the law. Under circumstances when an order for a passenger to leave can be justified then the Captain's word should be law; but never when there is no good reason for the passenger to be ejected; even if it would allow the captain's "friends" to fly in their place, because they are supremely important, and customers are just annoying dregs to be pushed off on whim.