The only reason to be against punching Nazis is if you're worried that it will erode our democracy and freedom of speech. You're thinking "First they came for the Socialists, and I did not speak out -- Because I was not a socialist." But what you're forgetting is that the "they" in that poem are the fucking Nazis! There's no need for a slippery slope. You can punch slave owners and you can punch Nazis. They get special dispensation to be punched. Like how Native Americans are allowed to run casinos. There's a history to keep in mind.
K: I'm actually not that concerned about the Nazi's free speech. As far as I'm concerned, we'd be better off if Nazis were never listened to again and Pepe the Frog got flattened like a tube of toothpaste under an 18-wheeler. But that's not what's happening. We've been giving white supremacists a lot of attention lately, including covering their little Nazi cosplay rally, where reporters flocked to show them sieg-heiling Trump. But they did that precisely because white supremacists love this kind of press. And they love looking like victims, because they get even more attention. Like a four-year-old who's pooped his pants and butt-scooted across the room while crying, screaming that the Jews put crap in his shorts.
A: OK, that is a totally fair point. They weirdly do love looking like victims, and it gets more eyeballs on them. But it's also just inherently satisfying to watch a group that is all about might and oppression whine like babies about being victims. For example, Richard Spencer, in his Periscope about the attack, claims both that it "didn't hurt that much" (because he's such an ubermensch) and also that he "probably suffered a minor concussion" (because he has to play up his victim status). And watching Nazis struggle to do those kinds of mental gymnastics is almost as good as watching them struggle to outpace Jesse Owens in the 1936 Olympics in Berlin.
Yes, more coverage of Nazi rallies means more people will be exposed to their hateful message, but you could say the same thing about Captain America. Watching Cap punch Nazis exposes more people to swastikas, but it also exposes more people to how smacking them around will make literally millions of people cheer your name.