Playing bad is inconsiderate
Here is what I mean: You get matched up with someone that is clearly not focused, and doesn't care too much and plays sloppy, dies a whole bunch early etc.
I have to say, that is very rude and inconsiderate. I'm so sick of people logging into ranked who play like shit and then they say, its just a game, or, oh sorry I was on the phone. Sorry I got distracted by something on TV. GREAT GO PLAY NORMALS.
This is part of the underlying reason for toxicity. You have and team that is not always on the same page as far as what level of seriousness ought to be brought to the match. That makes the players who are ready to focus and play feel cheated out of their time.
I don't think Riot understands this at all. They just want to put blame on the result of the above mentioned problem. The result being, toxic language etc. But that is not the problem. Only a symptom, and anyone that doesn't have a small mind should clearly see that. The fact that Riot doesn't seem to address the problem in these terms tells us that they are A) Stupid people or B) they think WE are stupid and they can just push their rhetoric and tribunals.