At the end of the match, after the photo, you can click on the name of the player you want and there's the option to report for a number of different reasons including Harassment.
But IMO you can just mute the lobby if you do not tolerate to much that kind of toxicity, and also learn how to kick, punch or headbutt when someone grabs you to knock them out so they leave you alone.
This does not excuses what the other player did, but to quit a game you like just for a random?
To me that seems like a win for him.