You're right that "aggregate market preferences might still gravitate towards state-issued fiat in politically stable context". 

I don't think any Bitcoin maxi has denied that the nation state has been a very powerful, albeit relatively recent phenomenon in human history that represents the current equilibrium. And to a great extent its power is derived from its ability to issue fiat.

This is not the point anyone argues with. 

What maxis say is that this equilibrium was a local maximum which is destabilized by the rise of truly decentralized money. Bitcoin, over time, “reduces the capacity of the world’s nation states to determine who becomes a Sovereign Individual […] and liberates the holders of wealth from expropriation through inflation.” (from The Sovereign Individual). 

It will thereby introduce a new operating system for the world, which transcends the current nation state model.