As a German I have a solution:

If we see a Nazi, we punch them. And with see, I mean specific symbols, clothing or other specific identifiers.

If I'm on a trump really, I should be able to punch the people in KKK outfits, the ones with swastikas, and the ones with old flags representing nationalism. And I should also be able to call the rest of them out.

I like this solution. It's a pretty straightforward one.