Toxicity after the game. Why is it allowed?

EDIT: I just looked at the offender's op.gg. He is still playing. I just want to say this is disgusting and unacceptable from Riot to let racism and hate speech unpunished. Being black myself, my parents told me horror stories of being persecuted, harassed and mistreated for simply being black. The fact that the reporting system will ban players for slighly passive aggressive speech, but a direct ticket with screenshots of blatant racist comments such a the N word does not even merit a ban makes me think Riot simply does NOT care about their players and improving this community.

Im bronze 2 and recently played a normal game vs a diamond 2 player. Somehow i won and after the game, in the lobby chat, this diamond 2 players started calling his team the N word as well as other insults. Then he talked about how we are all random and linked a twitch clip supposedly about Scarra saying that he is a beast at the game. He kept spamming how we all suck at the game and how good he is.

Why is this behavior allowed after the game in the lobby chat???? Its not the first time i have seen players use the N word there and they have not been punished when i report them.