Earlier quoted context omitted.
A 51% plutocracy is still a form of state governance that qualifies as fiat money and effectively can destroy the value of your coins if you resist. It is really no different than the government fining you for disobedience. There are philosophical theoretical arguments against this, not pragmatic ones.
According to this definition, is there any possible form of widely-used money that isn’t fiat money?
There used to be 100+ years ago such as gold and silver coins where if you were able to remove them from Country A to Country B, then Country A could no longer enforce such financial penalties against you. This is what many of the cryptocoins _wanted_ to be.
It needs to be a hard currency that leaves you immune to monetary policy and fines unless you are physically within the jurisdiction of the country.