The dollar or any fiat is essentially backed by assets held by the central bank. Thus the value of the dollar is determined by the assets that it is backed by. I think perhaps what you mean is that Bitcoin has no asset backing it, like the dollar or other fiat. But that is because Bitcoin is largely an asset, not really a currency.
Not even that nowadays. Since 1971 that shiat currency is backed by millions and millions of nothing! The only thing keeping value is the sheep (the people) that were fouled by governments believing that what the state says is valid. So, the value shiat money has, is backed by trust... Trust can't even be quantized, for fuck sake. This @Snowshow is defending who know what! He's just trying to make a non-sense point of his opinion which has as much value as his shiat money!
Let me repeat what I already explained. Fiat money is numbers that represent the quantity of debt (loans) created in the banking system. Numbers are not suppose to be backed, but debt. Debt is backed by collaterals. Try to educate yourself instead of just repeating nonsense conspiracy theories.