I am definitely a big supporter of the K.E.N. Campaign. If you don't know what it is, The K.E.N. Campaign is anti cyber-bullying and about "Keeping Everything Nice" in gaming. Here's the video for the campaign:
There is a false bravado that is created by the anonymity of the internet. Being a bully online isn't brave at all; it's cowardly. It's easy to be a troll, a bastard, or just plain mean on the internet. No one will ever know who you actually are and the people receiving your abuse are probably far away from you. Assholes are all over the web and the K.E.N. campaign is about isolating them.
In real life, I find that it is very rare to run into someone who isn't kind. Assholes may stick out in our thoughts and memories, but in reality the vast majority of people are friendly. In gaming, it is much the same way. Perhaps the proportion of assholes is greater due to the anonymity that exists, but the majority of gamers are nice and just trying to have fun. The assholes are the ones who stick out, but they are definitely the minority by a significant margin. If we make it clear that being an asshole is unacceptable and leave them isolated, it will be possible to defeat them.
It's not about fighting back; it's about being the better person. If you run into an asshole or a clan of assholes, fighting back will only encourage them. Just mute them, and if you feel comfortable, announce that you are doing so. If they are picking on someone else, just be a friend to that person. Simple as that. You've made it clear that cyber-bullying isn't going to be allowed to be effective while you're around. If all else fails, just choose not to game with that person or those people who are being assholes and leave the lobby.
Here is something that I feel is a misconception about the K.E.N. Campaign. The campaign is not about making the online community a place where one has to be super friendly all the time and everybody gets a trophy even if their a shit player. You're allowed to get upset, to still be competitive, but it just should never lead to bullying. Ultimately the goal should be to have fun while gaming, not boost your ego on the back of someone who is at the end of your mic.
Thanks for reading and Keep Everything Nice.
Link of interest: http://www.nixiepixel.com/protect-anonymity/
Nixie Pixel does an excellent job discussing the issues raised by anonymity on the internet and why it is a necessity even with the problems it helps to create.