A 'Government Put' on Bank Debt: Sorry, I Still Don't Get It

The very smart guys at Baseline Scenario say:

Once investors figure out that bank debt is not safe, they will refuse to lend to any banks, and we are back in September all over again.

Review the bidding: this is "regular debt" we are talking about, not guaranteed deposits. These are creditors who loaned against a limited liability entity, with the foreknowledge that their claim was limited to the value of the assets. Or was this their foreknowledge--could be rather that they loaned, thinking, "not to worry, we've got a 'government put'--if anything goes wrong, the taxpayers will just bail us out."

Did they in fact? In the first place, I don't think they did. In the second place, I would like to think they were fools if they did.

In either event, why should it affect new lenders? Even if the old lenders were somehow misled, the new lenders would come in knowing that they had no such guarantee--and price the product accordingly. Is that a problem?

Or is it the policy of the sovereign that (bank?) debt never bears downside risk?