This is BS. If the kid knows he has to stop playing at 9pm and it is 8:45pm and they start an hour-long game, how is it the parents' fault when the kid is forced to get off at their normal time? I'm sure the kid realizes what time it is and what time they start and are just hoping to push the boundary. This has nothing to do with parents and everything to do with the kid taking it upon themselves to be responsible for their parents' rules and their commitment to the other players.
Also, in no way ever are parents going to care about other people in an online game when they are making demands of their child to stop playing the game.
Basically, STFU League of Legends whiner.