I think the idea is just that they deserve it, even if it's (rightly) illegal.
I don't see that as problematic as long as it doesn't translate into policy. There are people I know who have committed far lesser evils than national socialistsm, who I still think would rightly deserve a swift punch to the face. This doesn't mean that I will punch them or encourage others to do so. It's just that if they happened to get punched, either by a person or some sort of cartoonish ACNE spring-loaded boxing glove gadget, I would probably laugh a little.
Enjoying the misery of terrible people is basically human nature. If you disagree, you're either lying or far more virtuous than the average person. The difference here is that what people enjoy on a visceral level can be extremely bad for society if acted upon. This is the reason why American courts tend to work better than a lynch-mob of Ethiopian villagers burning alleged potato thieves to death.
So, I find it hilarious when national socialists get punched, but I'm against it as well. Is that a contradictory position? I don't think so, but you decide!