Screw setting a good example. I would have dragged the MF out of the room by the ear, & let him know in no uncertain terms that he has no right to embarrass you in front of your students. Actually, that would be a better example to the kids, to show them that NOBODY has the right to humiliate anybody.

And then ask him to explain why he didn't show up earlier & do his job so you didn't have to break the rules by doing it for him.

__________________
Plug me into somethin'

If the theory does not conform to the facts, then the facts must be discarded.

No good deed ever goes unpunished

Never argue with an idiot. He'll drag you down to his level, & beat you with experience.