And that the founders had zero foresight to assume weapons technology would advance significantly beyond muskets. I mean really, do people think they were actual idiots?
To be fair, I doubt that they expected that nuclear weapons would be developed, and I'm sure they wouldn't be okay with chemical weapons either. But that's the strawman argument.
After all, the 2nd amendment was written at a time when civilian ownership of warships was okay, so I don't see how it shouldn't extend to all arms—past, present, and future.