I got that many times when a relative said something rude to me, and I answered right back. In the past I was told how rude I was, at which point I would parrot word for word what was said to me and ask.

"You don't think that was rude from them in the first place, I am answering in the same manner they talked to me. If they don't want it, then they should learn to talk nicer to me in the first place. Instead of assuming they can say whatever they want and get away with it.".

Interestingly, in the last decade my relatives have been a lot more polite with me when we talk.

I'm not telling you how to behave, I'm just saying that if you had thicker skin you would probably make more money, so another way of looking at that is that you're paying a premium for the luxury of being able to be, let's say "honest" then, instead of rude, to your customers.

I understand that and agree, but yes, I ascribe a high (societal) value to telling people when they're being rude, because I think to do otherwise is to enable them.

Besides, people like the customer in question come once in a decade (to me, anyway), so it hasn't been a problem.

> I'm just saying that if you had thicker skin you would probably make more money

In this case, I'd pay money to not deal with a customer like that.