I've had cats all my life so I'm pretty good at understanding cat behavior, the cat is simply play fighting with the kid, as if he was another cat. (which of course can get rough, but the cat means no harm)
Then the kid gets angry and hits it and of course THEN the cat gets angry haha.
The parents shouldn't have let the kid play fight with the cat.
Edit: youtube comment says "It's not the kids fault. The mom was egging this on from the beginning. She tells the kid to "hit it" in Russian."
Then when the kid gets attacked they keep laughing.
Such bad parents.