Riot "enabling" this sort of behavior.
It's good to see that the guy who, at the exact game start, said to me "Nidalee, I hope everyone you love dies", is still actively playing games, even after I, and I assume everyone else on my team, reported him/her.
Good to know that Riot is indirectly supporting these types of behavior. There is no reason or argument you can tell me that this should not be permanently bannable. No place for behavior like this to be in the game. And no, muting that player doesn't help. You shouldn't have to resort to muting just to not read what such a player says.