Downfall of Mute Button

As a heavy advocate for hitting the mute button for players everywhere, I'm at a complete loss as to why we are not allowed to mute pre game and post game.

Why is it that we can mute incredibly toxic people IN game, but upon hitting the post game screen, you are immediately exposed to all the people you had muted, screaming their profanities and insults and death threats? I shouldn't have to tuck tail and run out of every post game screen to avoid the inevitable continuation of toxicity.

If I have a bad game and ToxicJoe3000 decides its time to tell me I'm a piece of fucking shit ADC who needs to uninstall and remove myself from existence, you bet I mute him. But, post game, I get to see him all over again, and can not do anything about it.

Why is that okay Riot?