That.

In US law, if you want to play that game, the aircrew have the legal authority to tell you to take your assigned/a seat, move to another seat, put a seatbelt on, or ask the captain to order you off the plane. That's it. The last one can be for all sorts of interesting &/or silly reasons (on the part of the captain) but it still happens within the context of other US laws protecting pax. There's a thread on here somewhere which quotes the relevant 2-3 federal statutes.

That said, a person would have to be a complete idiot to try and play that game even when in the legal right. As @bitterprofit says above: document, comply under (at most) *verbal* protest, and then sue later. The reality is that if a crew in the US decides someone is X,Y, Z problem then it doesn't matter what the law says: they will have that person bounced. Police in the US are only to happy to use violence to do the airline bidding, as are far too many wannabe heroes. IMO it's more important to keep control of a situation and document it than it is to escalate it into the unpredictable.

Obviously, YMMV. Literally.