Why is toxic chat a higher priority than toxic play?

Got to be honest, there's practically nothing someone can say to me in-game that will get me riled. Basically all they can do is either personally insult me which is irrelevant because they don't know me, or they can criticize my play, which, even if they're being a dick about it, would have a grain of truth to it for them to even say it. I can also mute and report after the game with minimal effort.

However, toxic gameplay like intentionally leaving, trolling, feeding, etc, directly affects my ability to play a fair game. I can have 4 assholes as teammates but if they're all trying to win as hard as me, the game is fair.

I really don't understand why Riot takes the position that toxic chat is more significant than toxic gameplay.

People can get pissed, and they can go too far in chat, there's no doubt. However, without proper context as to what drove them to that point, I don't think you can ban just based on a chat log.

However, people who will gamethrow, especially in ranked, are an absolute cancer in this community, and really there is no circumstance or situation or context for that behavior. It is never acceptable, for any reason, and really if you come across someone who is intentionally griefing their team, you should start with a 2 week suspension, then a ban from there.