This is not the fault of any passenger.

The airline ceased to be civil when they shifted from an auction, to inviting police power on board. It was morally wrong for them to do this, and it was even worse for the police to agree to it.

There's no ethical, legal, or contractual argument for what the airline did; or the power they claim to have in this letter. They do not have the power to deplane people for the reason stated, their contract lists out numerous reasons for passenger removal but this is not one of them.