Smurfing isn't such a bad thing as long as the person smurfing isn't doing so to be a jerk to others. A few of us do so to help out the few new comers this game gets.
I assume you reported them after game? You might try sending in a ticket as well. Hate speech isn't tolerated and player support can force a chat restrict for such things.
This sadly is becoming more and more common place as things seem to be taking a turn for the worse.
Bear with the rest of us and Riot might, maybe, possibly fix things some day.
I just had a kid and his cousin tell me and everyone else in the game to 'KYS', two games in a row.