In other words if copper stops being used as money it still holds value as copper. You can melt down the coins and make it into wire or pots or waterer else people buy copper to make. Economists argue that these types of things don't make good currency because then the currency is effected by unrelated things like the copper industry. One would not want an entire national economy to fluctuate in value due to the ebb and flow of one industry.
The issue with a copper currency is that any actual unit of copper has intrinsic value, maybe very small, but it has it. A coper coin has the value of copper in it in addition to it's monetary value unlike a dollar bill or a bitcoin. An individual bitcoin has absolutely zero intrinsic value because an individual bitcoin is just a ledger entry in the bitcoin system.
What you are referring to that has value with respect to bitcoin is the entire bitcoin system, not an individual unit of that system. If we remove the monetary value of individual bitcoins they would have no value at all, just like the dollar bill, but exactly unlike copper.
Does that help?