It's the same reasoning the Marxists have for attacking Vidya, Tabletop, etc. Escapism leads to people not embracing the revolution. As long as you can say "meh whatever, I just want to Grill" and not drop everything and join their cultural revolution, their cultural revolution is missing out of people who would otherwise join them.
And if you wouldn't join them? Well, Mao teaches that any institution that cannot be changed to serve the interests of the revolution should be destroyed so the enemies of the revolution cannot use it.
Remember, the goal is to either get you to join them, or to make you fucking suffer because people who won't join them are traitors to the revolution and should be hurt -- and ultimately, put in gulags and worked to death.