I would've just belted the hell out of him. Kids should learn where the line is and stay behind that line.
A wise man named Russel Peters once pleaded with white people to please hit their children.
Both the entire truth. My mom beat my ass when I got out of line as a kid. I'm glad she did too, I look at kids these days and thank God every day I'm not like them.
This parental blaming is horse shit. When you hit 6 years old you better start learning that you are a person and you are performing actions, with consequences. It's on YOU as much as your parents, you are a person, start acting like one.
And if you can't do that, you get a leather belt on your ass for 15 minutes, then you get locked in the bathroom. I was never sent to my room, I was sent to the bathroom. Why? Because there are no toys, no super nintendos and no TVs in the bathroom.
Your parents make the rules, you follow them. It's their house, the end.
EDIT: In regard to the kid screaming "FUCK YOU" at his mom, I would pay a kid at his school to kick him in the balls. A kid hitting a kid is nothing illegal.