If the passenger left the aircraft and then returned to his seat as I’ve seen reported, then he probably violated a number of protocols that made him an “unruly” passenger without even knowing it.
After being beaten he did reboard. He did not return to his seat though. There are pictures of him appearing dazed and bloodied standing in the plane. His attorney says he has no recollection of reboarding. Understandable suffering a concussion. Bigger question is how was he allowed to get back on.
He returned after getting the crap beat out of him. Does that excite you? Make you giddy and warm in an erotic manner? I’ll bet so.