Buying a ticket doesn't mean you own the plane, and the Captain (or owners or any legitimate authority) has every right to ask you to leave if for any reason he believes your presence affects the safety of the craft or the other passengers. He doesn't even have to justify it, he's the Captain and its his call.

BUT, and there's always a "but", isn't there? The operators of the airline should not be ejecting (and perhaps seriously inconveniencing) paying customers simply because they have made a scheduling error or screwed up some management decision. That is their problem, not the passengers'. In a case like this, if they could not find volunteers willing to relinquish their seats, then they should have booked their employees with another airline, or even chartered a special flight.

The crew of the Titanic had every right to tell the passengers that women and children had first right to a seat on the lifeboats--tradition, Law of the Sea, human decency, whatever. They had no right to lock up the passengers from Steerage down below until all of First Class had been comfortably accommodated.

I will concede, that reluctant passenger was a bit of an asshole about it, though.

PS. I wonder if that unruly passenger ever caught up with his luggage?