To be clear, the Co-op isn't going to withdraw from banking tomorrow, so there is no reason for Co-op depositors to feel they are going to belefthighanddry.
The reason the billionaire oligarchs feel it is a legitimate fear that they could belefthighanddry is because it will take many months for them to sell their stake: the sale would require regulatory approval and also the unwinding of the complex network of international companies through which they own their stake in TNK-BP.
U.S. national security is dependent on those folks being able to operate with confidence that folks back home have their backs, so they're not just left out there highanddry, and potentially put in even more danger than they may already be.