Why does Riot punish "toxic" behaviour?

Why does League do this? People use the mute button if they don't want to deal with someone's insults. So why does Riot promote censorship? Punishment in a video game? I am sure everyone gets heated in games and only some take to chat to vent, that still does not explain the sjw attitude Riot seems to promote. And it's not just Riot, so many game companies are doing this as if they either have too much money to spend where they spend it on unncessary "forced discipline" or are compelled by some sort of butthurt philosophy? Secondly, how does the punishment system work? Do you first get chat restricted? Then a 7 day ban? Then 14 days, permanent? Do they punish you by analyzing one game?
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