Yes. I don’t support the use of violence, and those who commit violent crimes should be prosecuted.

That being said, there is a very real difference in scale between a punch and assault with a lethal firearm.

I can't speak for the OP, but I think "punch a Nazi" is totally unacceptable.

A related example: Antifa.

When a group expressing an extreme ideology begins to use violence against those who oppose it, is it acceptable to use violence in retaliation?

Historically, the answer is "after a while, yes". But it's a slippery slope towards becoming that which you oppose.