When people talk about punching a Nazi, they mean that they want to assault someone for holding views that they don't agree with. Yes, I know what the Nazis did in the 1930s and 1940s and yes, it's shocking to see Americans carrying Nazi symbols and praising Hitler. But that does not justify taking the law into your own hands and taking it upon yourself to punish the Nazi.
The meme of the moment is that "It's ok to punch a Nazi". This is often accompanied with the cover of Captain America #1 punching Hitler or something similar. But there's the thing.It's not World War II and you are not a comic book hero.
And who counts as a Nazi? Yes, it's easy to point to the idiots carrying swastikas but they don't carry them every day. Are you planning on hunting them down? Then will you go after Nazi sympathizers? A friend of mine was recently named in a Facebook posting as a Nazi-enabler for making the same points I'm making. This post called for violence against several people. I know other people who insist that anyone who didn't vote for Hillary Clinton is an Nazi-enabler. Where does this end?
Last weekend an engineer was fired from Google after sharing a complaint about Google's diversity programs. He was not against diversity but he did suggest that, possibly, women are less likely to be attracted to engineering as a career. He even backed this up with solid figures (although the links were all removed when his document was made public). After his firing he complained that he has been labeled a Nazi and received death threats.
This also seems to expect that the Nazis won't hit back. They will. Violence leads to more violence.