a perma ban in any game to which you spent money and did not abuse / hack / cheat the system is utterly disgusting.
if someone is toxic on chat, disable their chats
if someone keeps feeding on purpose disable gaming with other players for a duration or put a condition to play 10 games with bots or some other crap
a ban, let alone a permaban is like giving a death sentence, which is a bit too much for the very small "offenses" that happen during a game of league.
Riot's philosophy is either extremely catering to snowflakes, controlled by snowflakes, or is a victim of social media attacking it for lack of defending victim mentality.
Riot, get a grip. banning an account WILL NOT prevent the player from coming back with a different account and flaming / feeding / cheating / etc on another account. even banning IP is not a thing anymore with proxies.
Find a better solution, this is utterly absurd, whoever is in charge of this system needs to go get a few courses in psychology and philosophy and maybe listen to some debates online to get a better perspective on how to deal with conflict.