Are you saying that usability does not need to be considered in the design of critical systems?

Human factors grew out of the need to build safe and error-resistant weaponry in World War II. Poor attention to human factors and user interface design was a factor in the Three Mile Island disaster.

http://en.wikipedia.org/wiki/Human_factors#In_aviation

http://en.wikipedia.org/wiki/Three_Mile_Island_accident#Huma...

With respect, to call this armchair usability and to imply that some users are just stupid is to completely misunderstand what usability is.