Punch him back!

Today I went with my kids to playground. They were playing with a big group of other kids and I was relaxing sitting on a bench and reading a book.
When I was there I overheard a conversation between a father and his son, who could have been about 4 years old.
I didn't hear what the child say, but he was crying and his father replied sayin: "How many times do I have to tell you that you have to defend yourself? Did that kid punch you? Ok, punch him back! Hurt him! So he won't touch you again".
I had to light a cigarette because this thing made me feel very uncomfortable.
We have the chance, as parents, to give to our kids a better world. We can teach them how to live together, how to respect others, how to behave when someone shows using violence his disagreement.
We have a responsability towards future generations, towards the environment our kids will inherit, towards what they will make of their lives as free men and woman.
I wouldn't ever say such a thing to my daughters. 
Instead, I am try to make them understand that there's no use in behaving unpolitely towards people, even if they make us get angry. I would like them to learn that disagreement is a natural condition in man, and that there are some people that cannot handle stress properly. I always tell them that peace is something we can create if we reflect and try to understand what is really important in life. 
I hope my girls will learn what respect means and will behave accordingly.