Friend got permabanned for "griefing"

My friend was in a ranked game and he was playing Malphite support. His ADC was a Caitlyn. The Caitlyn was in the jungle for the first 15 mins of the game. My friend stole a few cs and the Caitlyn had 13 cs at the end of the game. My friend didn't type anything in-game, flame or not. My friend even was one of the highest damage dealers on his team. The Caitlyn and the Lee Sin on their team (presumably were a duo) reported my friend and he got permabanned, he did not even get a temporary suspension beforehand. My friend has only gotten temporary bans from leaving early due to real life issues. The anger of losing in a competitive match may have spurred some anger from the team, however, it is not worth it to actively try to put someone's hard-earned statistics and money down the drain.

Riot shouldn't have even gotten banned and if he deserved it he should have only gotten a temporary ban. If someone were to get reported and banned it should have been Caitlyn since she wasn't present within the lane for over half the game. The friend quote said that he had gotten banned for "stealing cs" but in reality, he didn't steal since she wasn't even PRESENT in the lane. Was he suppose to not take any cs since Caitlyn wasn't even in lane? This shouldn't have been a ban at all but perhaps a smaller punishment. I have also posted this onto Reddit and hope that riot lifts his perma ban.