For those who have gotten banned and are convinced they did nothing wrong in chat do this
Check your chat logs
Check your chat logs a second time
Check your chat logs a third time
If you were consistent in either calling your teammate out continually (see support teemo troll thread) or somehow saying something along the lines of "Shut the fuck up kid you're trash" congrats you most likely deserve your ban if not:
Check your chat logs a fourth time.
Check your chat logs a fifth time.
If EVERYTHING you said was NOWHERE near offensive- you're lying.
You most likely said something offensive or retaliated and probably deserve your ban because in every "STUPID RIOT I DON'T DESERVE MY BAN" thread I'm seeing, they deserve their ban imo and the system seems to be working fine.
Check your chat logs a sixth time.
If you still can't find anything offensive please stay out of this game. You can't differentiate between good and bad behaviour.
For all those that actually realize they're toxic and turn around-CONGRATS. We like you.