Frankly if it would be me I would have had the F/A advise the PAX that they will be subject to a little meeting with the FEDS at the destination for FAILURE TO OBEY A CREW Members instruction....and then let him stew for an hour or so...after all the the aircraft door was closed and was on an active taxiway...then upon arrival tell him he had better get booking before the COATS get to the gate........
Anyhow the response the CA gave was quite appropriate and made the point...maybe the other PAX got an education of what it takes to get their a$$$es in the sky and to the destination in the process.