I was watching Tarzaned's stream today. He is undeniably skilled, but today, 3-4 games in a row he spent the entire game furiously insulting the teammates with words in a complete unreasonable way, raging with every single mistake (most of them not even being objective), and going AFK or trolling in his challenger account with the ridiculous "L9" meme.
He has 4,000 people watching, some or many of them are aware of the immaturity, but a big portion of these are kid-teenagers that will mimic the behavior.
I know it's difficult to control this because they might not type as much in game, but I wanted to put the idea there because it's getting out of hand and I'm pretty sure it's affecting the community significantly, when the most influential streamers are these immature and toxic. They are arguably the biggest and most constant reference for players. What can you do?