Mean people always have to ruin things for everyone. They're miserable, so they have to drag everyone else down with them. And thus, they plague humanity as they have for hundreds of years. Dealing with mean people is a common conundrum that most of us have to face in our lifetime. There's always that person that just won't be nice, who has that sour demeanor that just won't go away.
It's always a difficult thing to deal with someone who always tries to bring you down. It's difficult to deal with nastiness, sly blows, rude behavior, etc. Logically, it's easy to say that the problem exists with that person, rather than with you. But still, it can get to you, especially they display constant rudeness.
Of course, mean people can include bullies, but sometimes, mean people aren't necessarily bullies. They're just mean. They're rude, grouchy, and will snap at people. They're negative people to be around and you dread being in their presence. There's always that one person.
The only thing you can do is lift your head and move on, pretend like it doesn't bother you. Because really these mean people just aren't worth your time or your energy. Yet that's easier said than done.