Insulting your coworkers and users is childish, and that's exactly what this post is. "More jarring were the people who insisted everything was OK" "was hailed as “efficient” (it wasn't)." In fact that's pretty much all it is. There are plenty of ways to complain without burning every bridge around you.
"More jarring were the people who insisted everything was OK"
I read this as simply being honest (in the "Dutch" sense). It wasn't like he was shit-talking his former co-workers, per se. He's just saying he had a radically different appraisal of technical viability of the flagship product.
Simply being honest doesn't mean you're not unneededly insulting everyone around you. He can say he had a radically different appraisal of the technical viability of mySQL without calling everyone he works with an idiot.
