Regarding rude people. I agree its best to kill them with kindness and/or just ignore them in most situations. Had a rude customer recently and I told them "Bye. Have a good day." Not liking that, they tried to escalate. I just drowned them out by repeatedly saying "Bye have a good day" over them talking shit. Wasn't the most professional way to handle it, but there were worse options. If the issue had reached management, saying "Have a good day" is a lot more defendable than saying, "Fuck off". A little CYA.

In other words, its harder to get fired for saying the former. But you and the customer both know what you're really telling them to do.