Reported as offensive language for being bad at the game

I am trying to teach my cousin how to play the game, and I'll admit he's not a great player, but he's lvl 5 and against bots. His team reported him for Offensive Language, and riot gave him a popup telling him how unsportsmanlike he was. I can tell you that I sat beside him the whole time while he was playing on this account, and he was generally positive, though he was exploring the game (twisted treeline), and was more interested in figuring out what things do than stomping a bot. Now he is really discouraged from playing the game, because even though you can mute people for being negative, it's really frustrating when the game itself is telling you how YOU are the one with the behavior problem. Is there anything that can be done to correct this situation? He's basically done playing with this game because he thinks the game hates him now, he is just a kid.