I can relate to the situation. There were days when I would have done the same thing, but I'm not proud of it. There was a time when I was a just an angry young man with a whole lot to prove, and unfortunately a lot of people suffered for it.
I grasp what you're saying about the guy. He obviously graduated first in his class from the white-trash school of parenting. What the child did was ugly, and all the uglier that dad obviously had no intentions of correcting him.
However, you still shouldn't have hit him.