As you note, I've already vented my spleen re: the 'unfunded liability' mantra.
As to the second, a one-dimensional 'starvation for cash' explains the entirety of fiscal policy since the mid-1980's. In other words, the policy of first reducing deficits, then retiring Federal debt held by the public seems to have irresistible political-economic roots, if not intellectual justification.
I raised this question repeatedly among political economists on PEN-L to little effect. My only explanation is that in the new era we have entered, financial markets and their underlying interests no longer desire that ultra-safe assets be floating around. Perhaps this is because investment options have broadened, or because state backing for plutocrats in distress (i.e., S&L bailout, Mexico, etc.) is assured.
mbs