Summoners Code Section VII.. So why ban then?
VII - Be Resolute, not Indignant
Remember that this is a competitive game, and, more often than not, the other player is just venting their frustration. Try not to take it personally. Everyone has a breaking point and everyone rages sometimes. At some point you may find yourself in the other person's shoes.
So... why do you ban people? If its nothing personal and everyone has a breaking point..... make a perma mute option. Stop crying.