How would your character react if he or she was publicly humiliated by a total stranger? What if it was a private humiliation? What if it was a friend and not a stranger?
I am willing to give some leeway for accidents and some weight to intentions, but not that much. In general I would react as follows.
Total stranger in public:
Step one, escape.
Step two, find out why they felt they needed to be such an ass.
Step three, revenge (if feasible... I'm not going to get myself killed over this unless it is mind-numbingly awful)
Total stranger in private:
Pretty much the same, but step one may be dispensed with and a replacement of punch them in the face before leaving might be put in it's place.
The steps would be pretty much the same. The only difference would be that that person would almost certainly no longer qualify as a friend. Depending on the severity of the embarrassment, they also might not be alive after step 3.