Everyone debating skill or whether or not this is an over reaction to his demeanor isn't looking at the fact that he broke Riot's Terms of Service. Every time you log in to play this game, you agree that you will play and act by their "Summoners Code." No player is above this regardless of skill, and all agree to it by logging in for a game. The code was put in place to maintain a healthy community, because despite the idea that some banter between players can be healthy and fun sarcasm does not read well and humor is often lost when tempers flare.
Adding to the above that he is effectively representing Riot and the game itself when playing at the championship level, the intelligent action from a business level alone would be to remove him to avoid the association between the league of legends and such negativity. There are numerous other potentially professional level players who do not feel a need to be so blatantly negative and inflammatory.