As long as both the critic and the criticized are supporting their arguments with reasons and engaged in dialogue, the outcome should be net good for everyone.
On the other, criticising a collegue for a mistake that is only obvious in retrospect is also poor sportsmanship.
2. "After you've dropped a bridge...": Until the investigation is complete, no one has any business assigning responsibility. (In fact, the investigation probably won't assign responsibility; that will be the job of the court system in the subsequent lawsuits.)
http://to70.com/why-aviation-safety-experts-dont-talk-about-...
Criticism, behind closed doors or strictly in the company of other engineers with the correct training and experience, is not dangerous.
Criticism shared with non-engineers amounts to second-guessing and degrades the trust of the public in the profession as a whole, which has tangible negative outcomes for everyone.
Imagine if every project you'd been on had another developer bending the ear of management saying "oh, that's the wrong editor...oh, that's not the right algorithm to use..."! It'd be awful.
For mechanical and structural engineering, both much more difficult and unknowable than software, it is of the utmost importance not to foment doubt and uncertainty in people who are by definition unqualified to properly understand the criticisms and weight them.
It works precisely until there is a scandal too big to cover-up.
Why do you think otherwise?
Also makes it ever so easy to bury the negligence and mistakes. Leaving the public devoid of trust and potentially with some very tangible negative outcomes. For instance:
"Yes your condition should have been identified, it's clear from the first X-rays in your history. No it's too late to do anything about it now, you just have to live with it. Put that in writing? I couldn't possibly do that."
Repeat several times.
Applicable to many of the professions in varying degree.