There's a difference between complaining and being downright rude. I'm not talking about when a customer asks for an explanation for why they couldn't save 50 cents on tater tots. I'm talking about when that person receives the explanation that oh, turns out the coupon was in english after all, and they got the wrong item (which is understandable, it happens. But what isn't acceptable:) so they start yelling at the cashier and taking out their frustration on them.
When a customers card or check bounces, it is NEVER the cashiers fault. Ever. They have NO influence over that. (I'm talking specifically about a card being declined for insufficient funds here, I'm not referring to when a card is incorrectly entered into the system or is punched into the system with the wrong numbers or is ran as the wrong type of card) Cashiers do NOT have the power to approve or deny cards, which is a concept some people don't understand. Their card is declined for insufficient funds, so they immediately start yelling at the cashier and telling them they did something wrong. "Invalid Card", "Wrong Card Number" "Card Read Error" may be the cashier, or more likely the computer-operated registers fault. "Insufficient funds" is NEVER the cashiers fault.
Also something alot of customers don't understand is just how much control the computer/register has. If the store policy is you cannot buy gift cards in the same ticket as anything else, then that's it. You CAN'T do it. The register will not let you, and no matter how badly the cashier may wish to oblige you, this breach of store policy is not even possible.
Like at some (maybe all?) wal-marts you can only buy tobacco at certain registers. Some customers throw a fit and demand an exception be made for them. It is literally not possible. The register will not let the cashier do it even if they did think this customer should be immune to the rules.
Talking down to a cashier is a sure sign that you're an ignorant piece of shit as well. And while the cashier in your story absolutely handled the situation incorrectly and you had every right to be angry, this is not the 'typical' situation of cashier bullying I was referring to.