stupidacity
A boneheaded action committed by one who should know better but goes ahead and does it anyway.
Stupidacity is as stupidacity does! May that dude rest in peace for running a stop sign in front of that semi truck that pushed him broadside into the train running alongside him.
stupidacalness
Stupid actions of stupid person or people
The manager was pissed at the stupidacalness of his workers...