Is anyone arguing for that, though? In either this thread or the last one, have you seen anyone suggest Richard Spencer shoulda been killed?
Richard Spencer should not have been summarily shot on sight. He shouldn't have had limbs removed, or broken. The person who assaulted him would probably have taken the rap, just like many protesters end up taking their arrests and getting their mugshots.
But all of the arguments in favor of him getting punched also work in favor of him getting shot in the head. Hey, Indiana Jones shot Nazis, too! We killed lots of Nazis during the war! Why not kill this guy?
Because even Nazi war criminals got trials, Nazi POWs were treated humanely under the law. Because we're the good guys.
If you think expressing Nazi ideas should result in physical harm, then let's have that debate, let's write it into law, have the police enforce it and let's give the perpetrators due process. Terrorists have rights, serial killers have rights, Nazis have rights. Because we're the good guys.
It would be much more satisfying to let vigilante justice take care of the monsters every time. But there's a reason we don't do that and the bigger the monster, the more important those rules become. We wouldn't need rules protecting freedom of expression if all expression were kind and popular. We created those rules specifically to protect people whose speech would otherwise get them punched.
You can point out that you can't yell 'fire' in a crowded theater, and I would say right, because that's against the law. We've decided, as a civilization, that kind of speech shouldn't be protected. If we're going to decide the same thing here, fine, put it to a vote, get it in writing, so that the punishment is carried out consistently and fairly. But don't leave it to whatever punch-happy person happens to be nearby.
But any reply of, "Why sympathize with a Nazi?" is a dishonest Straw Man argument, and you know it. Demanding due process and fair trials isn't sympathizing with criminals - remaining civilized in the face of monsters is the foundation of everything good about the world.