You know they'd have a point if they were talking about Bitcoin and gold, but they're not - because if you don't get understand what underpins the value of fiat, or pretend it's the same - then you have an agenda to push.
Fiat has value because it's legally recognized by governments that issue it: it extinguishes tax and debt obligations in those jurisdictions. This makes it markedly different to any other of the commodity items listed: my government will only ever tax me fiat currency, which is sufficient to extinguish those taxes and fulfill debts. I can't be ordered to pay them in gold, or bitcoin.
Imagine if every merchant came up with their own currency and forced you to pay them in it only. Wouldn't a global currency be a lot more efficient & frictionless?
Fiat has value because it's legally recognized by governments that issue it: it extinguishes tax and debt obligations in those jurisdictions. This makes it markedly different to any other of the commodity items listed: my government will only ever tax me fiat currency, which is sufficient to extinguish those taxes and fulfill debts. I can't be ordered to pay them in gold, or bitcoin.