And people who make that argument are idiots--it necessarily implies that if everyone were to magically switch to Bitcoin overnight, then every military in the world would be abolished at the same time as unnecessary. It makes no sense to allocate anything larger than exactly 0% of the military's emissions to the "cost" of currency, because that is how much effort the military spends on enforcing its value.

(You'd actually have a stronger argument trying to allocate a portion of the police budget to it, as it's the police forces who would enforce payment of debts in government specie, not military, and in the US at least, the military is prohibited from acting in a police capacity.)