Why Banning Players only hurts Riot in the end.

So, you dish out timed and permanent bans for folks, those people create new accounts, at least some of them are upset about the ban or just general state or how things are handled, troll and flame your new player base. I'm willing to bet a good deal of potential new players are completely driven away from playing the game because of being forced to level up with the enraged people you have banned.

Trolling is far more acceptable than flaming. You can troll pretty much however you like as long as you dont say a naughty word. There's a word filter and mute option for a reason, so that problem is already fixed within the game. The real problem lies in people trolling the crap out of their teammates through their actual play/decisions, many of which go unpunished.

tl;dr Riot is foolish. Troll however you like, but dont swear.