"They talk about the past 200 years of central banking and seem to forget the thousands of years of human economy before governmental central banking, when money was actually backed by a scarce resource."

Please check your facts. For the majority of human history, money was not backed by a scarce resource, but by government power.

For example, there was no guarantee in the Roman empire of exchanging coins to a certain amount of gold or silver, and the value of the coins in the Roman empire was largely unrelated to their material value.

To make that more precise, the reason that precious metals were used in coins was to prevent forgeries. If C is the cost to produce a coin or piece of paper money, then its value will (with very few degeneracies) always be in the range between C and f*C, where f > 1 is a factor that depends on the level of anti-forgery technology, and on the efficiency of law enforcement for tracking down forgers.

After all, no government in their right mind would produce coins whose value is lower than or equal to the cost to produce them - that would just be a nonsensical work. Therefore, the value is larger than C.

However, the higher the ratio between value and cost of production, the more attractive the coin or paper money becomes as a target for forgers. So raising the cost C of production makes it less attractive to forgers.

Interesting side note: If you actually look at the (unfortunately scarce) data concerning inflation in the Roman empire, you will see that as inflation pushes the real value of coins down, and the nominal cost of production of the coins up, the government eventually reacted by minting new coins with adjusted production costs (by reducing the amount of precious metals in the coins, or by creating new coins with the same amount of precious metals, but higher nominal value).

It is quite unfortunate that folklore has the causality between minting coins and inflation exactly the wrong way around.