...it was the fact that the controller decided that the rules didn't apply to him.
Any controller that's ever said "good day" on frequency has decided that the rules don't apply to them either. At least by US standards, that's a non-essential transmission, and therefore "against the rules". Let's fire them all.
You don't trash an expensively licensed person for something like this. Well YOU might (which is why you aren't a manager!
You haven't dealt with FAA management much, have you?