Do I believe in punching neo-Nazis? Not really. Would I care if a neo-Nazi got punched in the face? Not really. Because who cares what happens to them? They're neo-Nazis! They're horrible people who deserve to have horrible things happen to them.
With that said, would I recommend punching them? No. But if for no other reason than they can probably punch back harder! I mean, have you seen most skinheads?! They're not exactly the type of people you want to provoke violence against. As such, I can neither condone nor condemn violence against them.
Of course, if you want a more "intuitive" opinion about the virtues (or vices) of "Nazi punching", I'd recommend this video by ContraPoints: