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. :)
Both conflicts are horrific, but what was their alternative? We saw what happened in Germany when few fought back, and that was just as horrific an outcome, if not more so (6 million Jews killed vs 300 thousand on the left side in the Spanish civil war, though estimates vary).
Tens of thousands died under Mussolini in labor camps and via execution, and the same would’ve happened under Franco in Spain (and eventually did, post civil war)
To be clear, I’m not advocating that any country rush to armed conflict, but history seems to indicate that it’s better to be capable of defending yourself vs. not having the option at all.
If you have examples of pacifism being effective against fascism, I’m quite open to having my mind changed. In fact, I would prefer if that were the more effective option, if evidence supports it.