You can't hit a button to stop someone from quitting the game. You can't hit a button to stop someone from running it down. You can't hit a button to stop someone from saying "Nah, I don't want to win" and AFK farming until you lose because he had a bad day is a rotten sociopath who likes to feel like he has power.
It doesn't matter how vile, twisted, or bigoted your chat is, it isn't even 1% as bad as intentionally losing the game. Get off your high horse.
If you decide you don't like your team because they're flaming, so you AFK farm until your team loses an otherwise winnable game, you deserve to be permabanned for first offense.
There should be absolutely no second chances for trolling, no exceptions.