Seriously, you're underestimating a motivated government's ability to use violence to either prevent transactions (by taking some of the multisig parties out) or to coerce a transaction (by applying multiple hoses to multiple people).
Say they capture your family. Would you not make a transaction to save your family? If you didn't they'd just take you out. Heck, a motivated government might just take you out after anyways! See how your "coins" are no longer your biggest problem under an authoritarian regime?
In the face of the KGB, you wouldn't be saying "but your violence can't solve this math problem" for very long. Not without that tongue. How many fingernails does a man need anyways? Trust me, that math problem's getting solved. With hoses. Real fast.
This is one of those conceptual exercises that falls right over.