Just an all-around poor judgment call from this drunk guy to let a boxer get a free knockout punch on him. But we hear alcohol can have that effect on people.
This is probably why you shouldn’t have friends that know how to box or even just keep a pair of boxing gloves lying around. Sure, they might be good to have with you in case a bar brawl breaks out, but the majority of the time they’ll probably just get you really drunk and convince you to let them knock you out. Because friends are assholes.