The steelman version of “punching Nazis is okay” is that one should not bring verbal arguments into a punching fight. That is, we assume that the Nazis are there to punch you, and if you prepare for verbal fight, well, don’t expect to return home unharmed.
But that guy didn’t just “not bring verbal arguments into a punching fight”, he brought a punch into a verbal argument.
I am not familiar with the specific case, my answer was meant in general.
EDIT: I think it was historically the situation that when Nazis (the real ones, i.e. the NSDAP Nazis, not the people who disagree with me “Nazis”) were losing a political debate, they often changed the rules of the game, and attacked their opponents physically (“pigeon chess”). Which is why everyone else developed a rule “if Nazis invite you to a debate, you don’t participate (or you come ready to throw punches, if necessary)”. No idea whether this is a fact or a myth.
But that guy didn’t just “not bring verbal arguments into a punching fight”, he brought a punch into a verbal argument.
I am not familiar with the specific case, my answer was meant in general.
EDIT: I think it was historically the situation that when Nazis (the real ones, i.e. the NSDAP Nazis, not the people who disagree with me “Nazis”) were losing a political debate, they often changed the rules of the game, and attacked their opponents physically (“pigeon chess”). Which is why everyone else developed a rule “if Nazis invite you to a debate, you don’t participate (or you come ready to throw punches, if necessary)”. No idea whether this is a fact or a myth.