On twitter, responding to a similar claim, I observed that the Warsaw Uprising (where some Jews did have guns), belies the notion that Jews simply having guns would have meaningfully obstructed the Nazi genocidal machine. To which the reply was -- well, clearly they didn't have enough guns. Which, given that the NRA's response to any gun violence is "there should have been more good guys with guns in the room", isn't that surprising.
Now, in a sense it is right to say that the reason the Warsaw Uprising failed is that the Jews didn't have enough firepower -- that is, enough firepower to singlehandedly defeat a modern state's war apparatus. But I think we should hone in on the precise claim being made here. When the NRA says "we need an armed populace to defend ourselves from potentially genocidal government", it can't be talking about a couple people with handguns in their house or even some AR-15s. The only way this logic works is if they think every social group in America should have at its disposal enough advanced weaponry to take out a tank battalion along with its air support.
That power is, should, and must be vested in states -- which means there is no alternative response to the risk of (domestic) state violence and oppression other than inculcating that state with liberal and rule-of-law values so that it can both have the capacity to defend itself against external threats while not using those capacities to oppress others. This is a far more plausible lesson to draw from the Holocaust compared to a world where we handout Stingers and Hellfire Missiles as Bar Mitzvah presents.