Speaking from my time as an assistant manager at a gas station, any customer who even started yelling, screaming, or otherwise verbally abusing one of my employees would have been shown the door by the police, and informed that her/his thousands of dollars would no longer be welcome at my store.
In my humble opinion, any manager or supervisor worth the title would have done the same thing.
In fact, I have, during my stint in management hell, 86'd numerous people from the property for that kind of crap. It usually came right after the cashier asked for ID and the person could not provide it on an age restricted purchase.
And my employees had standing orders to first call the police, then me, regardless of the time, if I was not in when the excrement hit the air circulation device.
Reading these stories on your site just sometimes gets my blood boiling. I served in management, and I just cannot comprehend how you can allow your employees to be treated like that. I certainly cannot fathom why you would either do nothing to discourage it, or worse, take the crusty's side.
Without customers, the store won't make money, but without employees, the store won't be able to open or exist.
Probably on the wrong site for this, but managers, stand up for your employees. If the customer is an abusive douchebag, remove them from the store, and tell them to take their business elsewhere. To all the managers out there: Good God, grow a pair. Where would you be without your employees?
--Johnny, the Homicidal Former Manager Turned Tech Support Slave