My guess is that both the diver and Musk desperately wanted to help the kids. The divers attack on musk (I believe attack is too strong a word, but sticking with your terminology) was likely motivated by the view that Musk was making things worse, not better, with impractical ideas. From what I've read of the case, musk's submarine was indeed not practical - for this requirement.
However, whatever the divers motivation, responding by falsely accusing someone of being a paedophile is vicious, uncalled for and indicative of being a giant douche. Apologizing and then unapologising - and doubling down on the false smears of someone way below him on the ladder - is more of the same.
You're claiming to know the motivations of others, but your record of accuracy is not great in this thread.
Building and delivering a sub with the intention to help, is never going to "make things worse" even if the sub isn't used.
If my colleague writes a program that ends up not fitting the application, I would never tell them to shove their code up their arse. Who would do that other than a giant douche?
Both the Diver and Musk engaged in a squabble in public, started by the diver, escalated by Musk. You're focusing too much on the contents of the insults, and deciding Musk's was not only the greater crime, but the only crime. You've pardoned the diver of any fault, and invented a squeaky-clean backstory to explain his remarks.