Why do people seem to go to amazing lengths to display incredible amounts of uncalled for rudeness?

The 2 biggest places it seems to happen are in high school and on the internet. I was just recently ditched by my 2 "best friends" for other people, and now they seem to feel the need to treat me like total crap in order to impress them. Seeing as they shut me out, I've decided to do the same, and I haven't willingly talked to them since. Then there's my class (the 2 people who shut me out are younger than me) who will sneak up on me, smash a chair over my head, and laugh at me. I'll turn around, ask what's your problem? Then I'll get the holy, calm down it was just a joke routine. Then there's the internet. I'm only really part of one social network, youtube, and all I do is comment. I'd say next to facebook, youtube is the worst. That's why I dont (and never will) have a facebook. I could post some completely innocent comment on youtube,and some jerk will look freakishly deep into it, find something insulting, and bash me down over it. so here I am not arguing and just asking the person to calm down, and they'll just keep right on cussing me out. I just find it hard to function in modern society whilst being constantly picked on and bashed down by people who feel the need to belittle others to enlarge themselves. What can I do to cope? (no rude comments, this place is pretty bad too sometimes)