In situations like this, if there is an aggressor (say the customer in this case) they expect a certain outcome. They envision how the interaction will go. "I'll be demanding. Employee will get upset, maybe a bit snippy. I'll yell at them and show them who's boss. Maybe even complain to the manager." But in turn they see a smile, complements ("Oh, what a beautiful Porsche you have!") and willingness to help. They are angry inside but it is hard to manifest it without appearing completely crazy.
I've heard of other stuff like this:
* In a dangerous part of town and see a bunch of shady people eye you up -- act crazy, mutter to yourself and maybe flail your arms. Friend liked to do this in a bad part of Chicago.
* Someone wants to pick an argument and is just contrarian no matter what you say. At first argue a bit, then immediately switch sides and argue against your old position (basically on their side). Also to make it fun, be kind of aggressive and angry at your old position just like they were.
* An aggressive panhandler is verbally harassing you asking for money. "No thanks, I'm good. Talk to you on Wednesday". Say it, as matter of fact as possible. Their mind will stop for a bit trying to process that, and it gives you enough time to walk away far enough.