A libertarian conundrum?

This question is asked by James Otteson:

Adam Smith argued that showing "too little spirit" can sometimes be a vice, because sometimes a situation can call for rising to confront a challenge--even when the challenge confronted is merely a verbal one. I think this suggests that there is such a thing as a "justified punch in the nose." If I'm right, it might present a limited counter-example to the first principle of libertarianism, which is an injunction against initiating violence.

For more see here. So is there such a thing as a justified punch in the nose?