Alternate reality. Just because you are a nice person in rl, doesn't mean your online persona in a pvp game have to be nice. If I can jump you, take all your stuff and leave you naked in the woods. I would be prone to do so in a game that allow such. But I could as well be prone to help you if I saw the same happened to you by a 3rd party (and they had better stuff to be had! :p).
Its a form of escapism. With the anonymity of the internet and an avatar to wear as a mask, you can pretty much act however you want with little fear it'll follow you back into real life.
There are some times when it can turn into a bad thing. I like a good fight, but also remember that I'm playing with fellow humans. Don't take the game too seriously. Have fun.
One final thought: When you know what motivates someone, you have a little power over them. For instance, if you're being "bullied" in game, changing your behavior can help. If its a killer who is doing the "bullying", then the more you cry and complain, the more satisfaction they get from it. If its an achiever doing the "bullying", you're probably leaving something out that's easy points for them.
Well, imho in games, and particular pvp games. It's important to remember its actual people on the other side. It's important to have grace in victor as well. Kicking someone that is down, or make fun of, ridicule etc, is very bad. In some games people use "gf" (good fight), but I find that can be a insult as well. If you a superior player and then gank someone that is much weaker and say "gf"... that is just being a dick. I would only use it if its a close call and the other player put up an actual good fight. Else I would just do a "gg" (good game), doesn't necessary mean it was good game for the other player. But he/she put him/herself at risk in the game for situation allowing itself to unfold.
Its important if you are on the loosing end of the stick, you know how to behave and act though. Start to curse at the other player, threating and so forth, not very good. It will make things much worse. An expression says "eat humble pie", learn from your mistakes and gain experience.
Stormfall is a bit disturbing, so much hate and dislike and people take things way to personal. Leagues get demonized and portrayed as villains by just play the game. I believe this is related to how much MONEY driven this game is. People feel it in their wallets when they take damage where in most other games, you just spend soem time, grind by playing and you retored to where you was.