As an alternative, if we assume that a significant portion of the left is armed instead of just a minority, Rojava would be a good modern day example of the realistic effectiveness of an armed populace, as they employ horizontal citizen militias to survive against both ISIS and Turkey.

The Spanish Civil War is another interesting example, as the initial response from the left/anarchists when the fascists began their coup attempt was made up of civilian militias formed quickly and armed with whatever they had or could source from a local armory, and they were able to effectively fight off the initial coup in almost half the country, and gather themselves up for a protracted conflict. It’s not quite as direct an example, as the leftists in that conflict we supplemented with tanks and airplanes and artillery from the USSR, but firearms were an essential piece to their resistance, and had the populace been more armed before hand, it would’ve been helpful, as they had trouble producing and acquiring enough through trade.

There’s a great series on the Spanish Civil War here that gets into the nitty gritty, if you’re interested. :)