While I understand that this is a competitive game, and people are want to get heated, there is a difference between talking trash in the heat of the game, and talking trash after you've won, berating the enemy team, and in general having the grace in victory of an overweight rhino. RIOT claims to be trying to turn this into a legitimate esport, something that people will take seriously outside of the player base.
In actual sports? You do this sort of thing? You're punished for it, and quite severely because it erodes the public opinion of your team at the least, and at worst the sport, the latter of which is the state this game is in. Where if you bring up league of legends to a non league player, they WILL point this sort of thing out, have pointed this sort of thing out, and have pointed out far more grievous things as well in the area of player behavior and generally being garbage to each other.
And just because it happens more at low elo? Or in normals? That's no excuse for it because this really shouldn't be happening ANYWHERE within this game if it's ever going to be taken seriously. And while, yes, LoL is taken seriously within the confines of MOBAs? That's still a niche. A niche we sit in. A niche that we'll remain in for some time because if the basic bad player behaviors can't be fixed? We'll never fix the more egregious ones.
I'm also aware that there's no simple way to fix this short of the sledgehammer approach, but i'm not really sure the sledgehammer approach is a bad one. Bring back an actual spam selector on the reporting function. Bring back actually punishing people with chat mutes for bming, insulting other players, and generally just being unable to show some class. We have an automated system for administering punishments... And yet it feels worse than the old tribunal. If it's actually better? Actually cutting down on the general count of people being terrible to their fellow man? Then the problem is infinitely worse than it already looked to be.