The reason that libertarian bitcoiners like to use the word fiat as a dirty word is that they feel that taking the dollar off the gold standard was an egregious act by government.    In my opinion, it was inevitable, because at a moment of crisis, a government would always choose to steal the gold rather than let the economy crash.  There was no way they would have let dollar holders run the bank and redeem their dollars for gold.   This is a flaw of centralized banking.

Representative commodity currencies also have a flaw in that the commodity must be guarded, and eventually, the commodity ends up in the hands of the guards or is stolen.   The gold backing Liberty Dollars was stolen by the government, thus it failed as a money system.

I think bitcoin can prove itself to be a superior form of money to either a government-issued fiat currency or a representative commodity currency, since it will be immune to direct government manipulation, and immune to theft from government or otherwise, if properly handled, because it is a better form of fiat currency.

I don't think it is necessary for money to have intrinsic value for it to work.  Obviously, US dollars currently dominate the global economy, and bitcoin is slowing gaining acceptance as a means of payment.

I just find it colloquial for libertarians to continue using the term "fiat" to differentiate bitcoin from government-issued fiat, when the original use was to differentiate gold-backed dollars from fiat dollars.