Earlier quoted context omitted.
You're implying that there are always back channels? What if they could effectively limit the supply of something? Can you buy a live sample of measles?
You're getting way off track here. The assertion was that the government is afraid that it can't stop you from spending bitcoins, the implication being that it can with cash. Bitcoin vs. USD doesn't solve your ability to purchase weaponized measles.
They can even do it automatedly, such as freezing the ability to withdraw or deposit funds electronically.