It's not often that I encounter mean people, but when I do, they baffle me. Why would someone be repeatedly mean--what makes people that sour?
I considered that with some depth yesterday, and as one consult noted, mean people are usually unhappy for some reason. Perhaps they have difficulty expressing their thoughts or perhaps there is a deep seated conflict they haven't resolved. It's difficult to know exactly why a mean person is mean, but it's not difficult to realize their unfriendly and mean demeanor makes situations uncomfortable and undesirable.
For the most part, it's good to face meanness with compassion, empathy, kindness, and care. It's also usually a good idea to give mean people some space if your attempts to understand or help are unsuccessful. And, if the meanness is dangerous, you have to do what you can to keep yourself and others safe. Onward.