sorry gremlin but i used to work in the drug rehab capital of Europe in a store and believe me, I've been involved in incidents with knives, bats, and various other weapons, even being threatened to be shot.
However, I always acted professionally, restraining them when necessary. I have never sworn at them or thrown a punch.
I wouldn't stoop to their level. We can always walk away if we cannot control the situation and use the panic alarms, thats what they are for.
Despite all threats of recriminations, not one ever attacked me after work, although one was foolish enough to follow me. He was dissuaded easily enough and went about his way.
If we come down to their level, we encourage them to come back and have a go, just for kicks every time they are bored.
If a guy had spat in my face, I would have grabbed them and detained them for the police, but then I am an instructor in various martial arts. If I weren't I would have called the police, the managers and anybody else to hand. I also would have made a bee line for the nearest sink.
As a union rep I would have argued for the lady who swore that that was extreme extenuating circumstance which should have been taken into account. But I wouldn't condone that action.