This article has a lot of arguments specifically about safety. And even then, unions can increase safety in some domain, while simultaneously decrease safety in other domain and bankrupt host airline.

Moreover, Sully, as senior pilot, was direct benefactor of the union system that exploits younger pilots, so his opinions should be scrutinized first of all.

A better analogy would be the company owner's son who "started at the bottom" explaining why a union is unnecessary.