Don't get me wrong, I'm not going to start punching Nazis myself (because I'm a cowardly motherfucker and I'd probably go to jail) and if I were a judge at a trial for that antifa guy I'd give him a guilty verdict for assault, because he did still punch a guy. But that's on a higher level. I wouldn't be chomping at the bit to report the guy if given the opportunity. And if someone went "I'm gonna punch a Nazi" at a bar to me, I wouldn't exactly trip over myself to stop the guy.
Well, at least out of any "but you'll only give Nazis legitimacy" reason, because what do I care about the feelings of Nazis or idiots who'd sympathize with them on the sole basis of them getting hate? But they'd probably get in trouble with the bar staff and authorities, so I'd t least try to talk their way out of them.
Now as political praxis, I admit the matter's more nuanced. Sure, institutionally legitimizing vigilante violence against certain groups opens doors to scary implications, but at the same time, nazis care shitall about democracy. Uncritically allowing them into the political mainstream will let them abuse a system they disdain and expand the Overton Window until they can pull back Hitler's soul from Hell through it, piece by piece. Adults don't do violence as constructive conflict resolution and it shouldn't be incentivized on a governmental level, but at the same time if Nazis wanna martyr themselves because they're hated for being Nazis, that's on them. They were already doing it anyway.
I don't know the right answer, is what I'm trying to say. And I don't wanna come across like I do. All I can do is have my thoughts on it and not actually have any influence of significance. But I can at least see where you're coming from.