I mean, I guess the argument here is "well, if the gov't goes crazy we still have weapons because 2A let us amass them". But in reality, the US government is unimaginably powerful. Like they could easily take control of all energy producing facilities everywhere, every major city, port, road, railroad, airport, hospital, etc. There are probably close to a million law enforcement officials in the US. And all that's to say nothing of advanced military, surveillance, and espionage capability.
Basically, the idea that 2A would let us protect any semblance of our current way if life is fantasy. The most you could hope for is to join a resistance and dig in for a generations long, probably species destroying authoritarian regime to run its course.
Obviously it's and absolute last ditch, not taken lightly and very undesirable. But, to have the option, is true sovereignty to me.