So the game of LoL that I got into today was pretty spot on for this topic. Played a game that we lost this morning that had a Blitzcrank in it. The reason I call him out specifically it he was singularly the worst played of the 10 champions in that game. He was also the only person in the game raging, at least, that I could see. I actively participate in the tribunal for LoL. One of the biggest offenses I see consistently in game is people raging at their team mates instead of playing.
And that is what it comes down to. No questions asked. If you are raging at anyone in a game, several things are happening that are causing the quality of your game to deteriorate and increasing the likely hood that you are going to lose.
For one, your not playing. You are standing still somewhere, typing out furious little sentences that everyone else is laughing at instead of controlling your champion and helping your team mates or farming for your levels/items. This is bad enough if it is in your base, where you are simply not participating. It is far worse if you are out on the map, sitting vulnerable somewhere.
Your not thinking clearly. You are angry about shit that doesn't matter, which causes you to make rash decisions and get into shit that you cannot handle. Stop, take a step back. Are you seriously raging over a few pixels on the screen. I understand just as well as a pro how important games can be to someone, but that doesn't mean you need to be raging, it hampers the thought process. If you want proof, go watch the streams that the pros put up. You can see their faces, hear their reactions. They don't rage.
You are alienating yourself from your team mates. They don't wont to listen to you, get dragged into your shit. They are playing a game, they want to have fun, you are ruining that for them. That is killer in a game like LoL that needs team communication above all. You end up on mute and the communication is gone.
Riot released some info a little while back. They have access to this kind of information, since they are able to see chat logs and all. While they didn't give exact numbers, they did state that it is easy to see a correlation showing that if you rage your are more likely to lose. And not only are you losing, your dragging 4 other people into it with you.