Lots of people say dumb things in the heat of the moment. Choosing to stick by it and not apologize is the confirmation dialogue for showing your character.
He afterwards paid someone to dig up more dirt and emailed media with further lies about the guy. At that point it kind of stops being "heat of the moment".
Yeah if every harmful thing constituted the "true character" of someone, we'd all be sinners. Granted, if a lot of harm is done, then it might be fair. (Cue the knee-jerk "isn't dragging a hero's name through the mud a lot of harm?"; I don't know, can you tell me what wouldn't qualify as a "lot of harm" under your worldview? Everyone knows the diver was a hero and if you have evidence his life is affected, pls share)
It's just negativity bias; considering the negative to be "more true" or accurate than the positive.
I have a friend of a friend who worked directly under Musk at one of his big ventures. Can confirm that Musk is a giant egotistical asshole, albeit a brilliant one.