We all know that guy that just rages in all chat about another player, just putting them on blast. Or the guy who says f*ck it I'm afk, after giving first blood. This is especially worse in the the lower elo. I'm currently plat 3 but I was bronze 5 when season 3 started. I know the struggle guys. If you want to gain some freelo try your best to defuse a bad argument; At times it's hard to hold back emotions when playing a game like League of Legends. Some people are hot headed. And if something goes wrong whether it be a bad play or someone harassing them. Instead of focusing on the game they turn their attention to that person. Which in turn makes them play worse. It depends on the person how much it really affects their play, but it for sure will. So make it your job to be the mediator. Solve the problem as quickly as possible. Make sure they know its just a game, and to try to have fun. Or if one of the players on the team is giving them a hard time, tell them to mute that person.
I'm sorry, but I don't actually have a lot of viable ways to stop the toxicity.. Unfortunately there is no 1 liner that is going to work on every single person to cool them down. But if you don't stop the toxicity quickly, it can spread through the entire team like cancer.