The fundamental principle of toxic behavior to your teammates: it hurts you!

Toxic behavior directed at your teammates during the game is self-defeating. It distracts your teammates, distracts yourself, hurts team morale, makes teammates less likely to help, and in general makes a bad gaming experience for everyone.

You're more likely to lose when you're toxic to your own teammates.

And yet, we see players being toxic to their own teammates during the game. I guess league players really have no control over their emotions.