Couldn't help but throw this out there considering this thread is still fairly recent:
http://news.ca.msn.com/top-stories/video-game-rage-violent-imagery-isnt-the-trigger-researchers-say"While rage stemming from video games is common, there are different theories about what triggers it. Some suggest it's the violent images in the games, but a 2011 study conducted by researchers at Brock University indicated that the most influential factor in video game rage is the level of competition involved. "
"Adachi concluded that people who played highly competitive games behaved more aggressively than those who played the less competitive games. "
And according to DG, most ragers are CoD players

Apply a little deductive reasoning and.....
I consider BEING competitive and PLAYING competitive as two different things though. Being competitive might be as simple as just wanting to outscore your friend. Or trying to go on a win streak with your friends. Or even maintaining a K/D, W/L, or SPM.
Playing Competitive on the other hand means dedicating time, skill, and practice/strategies/callouts to win money against other teams doing the very same. And in this definition, I consider fighter games and MMO's to be a higher competitive level than CoD because there's a much higher player base dedicating their lives to perfecting the game/combos.
The problem with CoD is, everyone you face in pub games thinks they're the absolute best at it so they talk **** to anyone and everyone, even if they're not good. If they have a high K/D but face someone higher than them, they will either play and dashboard if they're losing or having a bad game, or they will back and out of the lobby before the game and look for noobs. That to me isn't PLAYING Competitive and it's simply people putting too much into their imaginary stats that they didn't really earn.