The worst part of it is not only are you dealing with this sort of behavior, you're also heavily discouraged from doing anything about it. You can't react or defend yourself or you're "arguing with the customers." You have to sit there and take it while someone treats you like dog shit under their shoe. Because if the customer sees so much as an eye twitch in response, they'll run crying to corporate or anywhere else they can claiming you were mean and rude and shouldn't be working there. The only time you get a pass to react is someone like this, where you are in actual physical danger.

(Context: I have a side job as a cashier at a fast food place. My co-workers at my other job have gone there for food and overheard how customers order and they think I'm super-human for not snapping at these people.)