You can't force people to be nice to you. Seeking to control other people is a pointless endeavor. Your problem is completely caused by a company handling censorship and not having community owned servers where bans are handed down near instantaneously. Further, in the defense of the person insulting you, they shouldn't be prevented from playing the game for being a jackass in chat. Chat ban? Sure. Full ban? I wonder how far you could take that in civil court to get your money back.
> Eventually I got sick of a game that committed me to 30-50 minutes of paying attention
This is your actual problem you just may not realize it. When someone is committing 50 minutes of their life to a stupid video game minor infractions like being a new player suddenly become a real problem. You are dragging down the team and you are ruining their experience. That's not your fault, really. Everyone starts out new and it sucks. It's also not their fault for being mean to you for legitimately ruining their game. It's a lot of time spent just to lose everything because one person doesn't know how to play. People aren't in the mindset of "help the noob" when an hours worth of progress gets flushed down the toilet for doing so. Call it the bystander effect, or whatever.
Riot would be better off making servers for more casual play. Most of the so-called "toxic" behavior I have seen in new games is because of long matches, wins and losses being strictly tied to progress, etc. The competitive aspect makes the game worse for everyone who doesn't want to compete.