I don't understand that either. Does anyone know why bitcoin would make such an attack more feasible? I guess maybe it's just that the IMF has plans in place to try to stop a traditional attack but hasn't spent much time thinking about bitcoin.
The only reason that Bitcoin would make an attack like this more feasible is because none of the IMF member countries own any BTC. To counter a "speculative attack," the country's commercial banks need to be able to sell their own country's currency for Bitcoin using a central bank. Solution: the central banks need to buy bitcoin (or mine their own).