Or someone else sell theirs. But, "He ought to find it more profitable to play by the rules" of holding gold. Such an attack on isn't as sustainable as it would be on bitcoin I guess, because they can't sell gold after they've sold it.

While I'm not going to be the source of a better answer than "He ought to find it more profitable to play by the rules," I hope we can find somewhere someone has explored this further than the whitepaper.