This is less “the chef sucks” and more “the chef just pissed his name on the local community center building”.

I’d argue there probably isn’t enough substance to the complaint yet (Space-X brand is probably still a net positive having him in front of the company), but your line of argument would cause a quiet brain drain from organizations, not keep them healthy with open discussion. The fact that this open letter was described outside of the company might be the only reason I might side with you.