It's happened to just about everyone who has been in a store or restaurant--an employee does something foolish or nonsensical, and the customer gets angry and lashes out at the employee. Maybe you've been the customer, maybe you've been the employee, or maybe you've just been a bystander, observing this happen. It's not a good situation for anyone involved.
It can get particularly ugly when the parties involved see each other as being One of Those People, and blame their behavior on that category of Other.
A simple perception of being in a different socioeconomic class can be enough to tip the scales, or a difference in gender, race, age group, etc.
Take this example--it may have happened over a year and a half ago, but it still sticks in my mind. I am "over it" emotionally--I mostly just laugh at it, but it remains in my memory as an example of this behavior:
I work at a gas station convenience store and manage the foodservice department (things like coffee, fountain drinks, hot dogs, sandwiches, etc.). Part of my job is making sure that machines have product in them to dispense to customers. Unfortunately, judging how much is left in a particular machine can be difficult. Some machines monitor how much has been dispensed, others have clear (or at least translucent) hoppers that allow one to see how much is left in the machine, but many have multi-layered containers for products to insulate them or protect them from light, evaporation, and pests, so the only way to tell when they're empty is to try dispensing the product. If I test something and it's ok, that doesn't necessarily mean that the next press of the button will also dispense the product.
I have difficulty recognizing all of the regular customers at the store, partly due to visual impairment, partly due to prosopagnosia, and partly due to the sheer volume of customers (I work at one of the busiest stores in the company). However, there are a few people whom I recognize because they're there at nearly the same time of day every day of the week, have a particular consistent quirk or physical characteristic, etc. One of these people is an unpleasant fellow I call "Spider Guy" in my head. He frequently wears a sparkly golden spider pin on the lapel of his suit, has distinctively bushy, scraggly long hair, and impossibly skinny legs (he sometimes wears tights/leggings rather than suit trousers). Sometime I have advance warning of when he's approaching the store, because he curses at the gas pump-authorizing cashiers over the intercom.
On this particular day, he wanted a chocolate flavored Steamer. Steamers are a latte-like product we used to sell at the hot drinks counter along with drip coffee and instant cappuccino. First, Spider Guy was angry because he couldn't locate the machine. He yelled at me because it wasn't in the spot where it "has always been," despite the fact that the machine had never been in that imaginary location because it wouldn't fit there and there isn't a water or electrical hookup there, either. I knew better than to point that out to him, and simply showed him where the machine was (and had been for the past year and a half, at least). Unfortunately, the machine was out of the chocolate flavor concentrate. Instead of informing me of this and asking me to replace it (which I could have done in a matter of minutes), he tore into me and called me a "four dollar an hour retard."
Now, really. What is that sort of behavior supposed to accomplish? What does a person gain by starting out with insults? And, more insidiously, why is "retard" an insult? I think that's what upset me most--hearing the word "retard" used as an insult.