I think all of that is irrelevant. He paid for a ticket. He didn’t create this problem. United did.
Perhaps they shouldn’t take people’s money until they are seated and off the ground. LOL
Interestingly, United’s CEO said today that this would NEVER NEVER happen again. Ever. That they made the error, not the customer, and he had every right to his seat. So, they understand that they have a big PR mess, and the dirt they dug up on him has only deepened their hole.