This doesn't have anything to do with New Zealand. Someone put forth the argument that small disorganized resistances would not prevail against large organized armies, for example that of the US. Yet we have examples of exactly such things happening. The fact that you explain how they happened doesn't dilute the point that they did happen.
I truly don't understand progressives sometimes. You (perhaps not literally you, pmv) speak of imminent fascism, style the more fervent among you as the Resistance, and bemoan the fact that Trump is in control of the nuclear codes. If Trump were to erect concentration camps and inter all manner of minorities in service to white supremacy or some other horror, don't you think that would involve exactly the sort of contingency that the 2nd amendment was intended to dissuade? Do you really regard yourself as helpless if that were to happen, since you think a resistance could never prevail against the US army?
If we had to call upon antifa to protect us from real and true fascists, would we want them armed or not?
That's not a terrible point. There certainly are hard-leftists who oppose gun-control for precisely that reason (and indeed some speak about needing guns to defend themselves against the police, never mind the army). But that's a dividing line between the far-left and the moderate-left. Most leftists don't speak in terms of an armed workers uprising violently overthrowing the state.
Don't actually know what antifa's attitude to gun-control is. They certainly like posing with the things, so it wouldn't at all surprise me if they were against it.
Of course, in many cases where revolutions occured it was with the assistance of parts of the military, as in Russia (most notably the Latvian Rifle Regiment) and Iran (parts of the airforce), so they had guns anyway. But those were countries with mass conscription.