A Report on Swearing in Online Games
A Next Generation article references an informal study done on the frequency of swearing on Xbox Live. From the study: "When you logon to Xbox live more often then not you will be greeted by a 14 year old that learned a new word on the playground that day, or maybe it's the drunken 24 year old who hates black people, gays and anyone who isn't in his frat. No matter who you are if you have played on live you have run into cursing and lewdness. If you look at the rating for the game you can see that it is intended for ages 17+ but parents don't care/understand/listen so lots of underage kids have [Halo 2]." Warning: links contain profanity.
If you can just goad them a little bit into cutting loose with their mouths, you are are halfway to victory.
Conversely, it is important to keep your own cool and your focus on the game. A few taunts when the other guy is down may help in keeping him down as you compound his anger, but this must be done out of strategy, not out of an effort to verbally 'get back' at your opponent.