Simple fact (from evidence available) is that the CC refused a perfectly reasonable request for a mutual seat swap.
(My bolding)
I haven't seen any video of the start of the incident, but did he request? Or did he swap and then advise of the swap when challenged by the CC? Perhaps not asking first is what peeved the CC and started the ball rolling. You never know what some people will take as an affront to their authority. As I've stated, JQ's Conditions of Carriage do not stipulate that you sit in your assigned seat, or that you request approval of or simply advise of any swaps. "You have to sit in your seat" is not backed up anywhere in writing that the Airline has stated or that the passenger has accepted.