> There were many private currencies in the 19th century that the government never claimed power over.

The fact that Congress chooses, for a time, not to exercise a power within the scope of its enumerated powers in Art. I does not in any way change the fact that it is an enumerated power.

> This move with regard to Bitcoin is merely Bank.Gov trying to protect its monopoly on the issuing of currency.

No, this is about punishing fraud in selling investments, not about issuing currency.