As an aside, I work inpatient psychiatry where it's not so much that they're always right as much as that it's pointless and even counterproductive to argue. In those situations you don't say "but this is a-" you say "I really wanna talk over the details of how to get you exactly what you want" then try to elicit the details of (to use this example) what they think a macchiato is.
Now, the reason I prefer working inpatient psychiatry as opposed to costumer service is that when they start yelling I get to say "oh, my apologies. I'll come back when you're more ready to talk about this!" and just leave. And then if they follow me to keep yelling...
The list of things I'm not allowed to do will always be longer than the list of things the waiter is legally not allowed to do. The waiter can legally just fight back, and I'm never allowed to do that. But the second they become significantly verbally threatening or physically threatening in any way, the list of things I'm not allowed to do to someone as part of my job suddenly becomes much shorter than the waiter's.