Do you think it's it okay to hit a dog in order to train him in this case?

My friends Lab is VERY well trained. He doesn’t need a leash when you walk him and he lives in Los Angeles. He’ll walk in front of you, but not too far, and he’ll always look back at you. He NEVER walks off the curb unless you tell him it’s okay. In order to train him not to walk off the curb, my buddy had to hit the dog.

What do you think about that?

I think it is for the dog’s own good. The dog will never walk out into a street and get killed by a car. It’s not like he hit him just so he does some stupid tricks or something.