Enter Frans Plugge. Whenever a customer would get into that mode we'd fire Frans. This was easy, simply because he didn't exist in the first place (his name was pulled from a skit by two Dutch comedians, bonus points if you know who and which skit).
This usually then caused the customer to recant on how he/she never meant for anybody to get fired...
It was a funny solution and we got away with it for years, for one because it was pretty rare to get customers that mad to begin with and for another because Frans never wrote any blog posts about it ;)
But I was always waiting for that call from the labor board to ask why we fired someone for who there was no record of employment.