It wasn't even kind of okay for the kid to slap his mom, but it's clear the kid is desperate to be heard and have his feelings validated. He's not the only brat in the room.
Humanity is fine right now. Society has a pretty large population of dregs--the anti-education culture and welfare queens--that we could stand to cut off like an infected limb, but most of us are fine. If the worst example you can come up with is an over-emotional and improperly disciplined fat kid then I think we're pretty well off, actually.