Managed to not choke my student to death.
Those of you who know me, I tend to say what I think, immediately.
SMA decided to go full batshit retard on the way back from event (to include three tries at course rules, 500' altitude deviations, setting up for the wrong airfield, and trying to break the wrong way...into tower) at which point I took the controls, taxied in quietly, had him shut down the plane, handed him his CFS pin, and walked away.
Haven't been that pissed/frustrated in a long time, had the knife hand all wound up, ready to crush souls...and realized it wouldn't be helpful. 1 cigarette, 1 beer, and 1 Marginal gradesheet later, I was able to debrief calmly....
Little victories...