Ranked makes people hate other people
I don't know why we try to pretend otherwise---idiots you don't know do stupid things to ruin the match, wasting your time and then lie about being Diamond on their other accounts, and think that giving any username is proof. Seriously, who are these morons who think we are all that stupid as if we will say, "oh, in that case I apologize for criticizing your stupid moves, since now that I know you are a Diamond player".
We are all fooling ourselves if you think tribunals change human nature, or a specific person's more...colorful nature. At best they are just hiding the fact that they want to rip into you verbally. So that's really it--feeling protection for the weak and thin skinned who need to get offended by any and everything.
Riot made a game that makes a person feel powerless very often.
Feeling powerless is a root cause of anger. This is not opinion. This a fact of human nature.
So of course ranked play will make people angry and toxic.