We have a saying where I am originally from: "mouth mek fi talk." I don't get to hit people who verbally abuse me. I have to either answer back and/or walk away. If I instead drop them with a hard right, I catch a case.
My first job right out of high school for one year before heading to uni was as a bank teller. We were taught that the customer is always right and not to talk back to them. At 18 years of age, I was able to exhibit quite a bit of self control in the face of angry and aggressive people. It's not rally that difficult.
It's called professionalism.