> namely that you can fairly dependably protect your cash by investing in physical security

If you've generated your private keys offline and store them on paper, that paper can be treated the same as cash of the same value, and secured in a similar mechanism

> there is inherently no such thing as a vulnerability that can be exploited at scale

Counterfeiting has been a problem for cash holders for a long time. It's definitely a more severe vulnerability for crypto holders tho.