Now let's get another real life example. You go and steal a pair of sunglasses from a store and they catch you. Meanwhile someone kills a person. Should you both get 30 years in jail? You both did something wrong. This is your logic.
I've seen people get banned for being negative and seen people who wish cancer to other for no reason at all done nothing to. You clearly don't get what is fair and what is not. Why is the punishment the same for both when one just wasn't happy while other wished death to another player?
You can't see what is all behind this policy. It is as always in favor of biggest part of the community that brings more funds. You see the quality of gameplay has really decreased during last seasons. Now all blame it on the dynamic queue, but the reason is other - no one cares about how good you play anymore. See, a person can play like shit but you don't have to be good to buy skins. So, it is important to keep players happy, not to make them improve in order to bring money, meaning that no one should be able to tell them they can't properly, because this might make them sad and cause them to stop purchasing from the store. Now, we have this system that punishes everyone for every time someone is offended, which is basically every 2nd game, because people have become little crybabies that say everything they don't like is toxic. And people like you believe that this is for the greater good of this community :D:D:D. All is done because of the money, now stop telling people to be responsible or anything like that.
And ok, flamers get punished because with their words they make the experience of the other players in game worse, right? Yep, Leaver buster punishes people that get dc or leave, because while they are not there they make the experience worse for the other players, right? But, what about players that constantly play worse but still go to ranked and become big burden for their team members. I'm not talking about just a bad games, there are many players that just troll, play terrible but are always there to make game worse. Why aren't they punished? Aren't they making the game experience worse for their team members? The difference is that there are way too many of these players and if you start punishing all it can hurt the funds. But you can always go and punish the small amount of players that aren't happy with these people entering to ruin their games and call it for the greater good.
Anyways, I don't really believe that this will make you change your mind, you are probably too naive. :) Good luck.