Why Doesn't Krugman Fear The Debt?

Crook asks:

I think Krugman is correct to argue against "fiscal austerity now now now", especially for the US. But Galston's view, as I say, is consistent with this. It's the long-term outlook they disagree about. I don't understand why Krugman won't more fully acknowledge the long-term problem. Why not give equal emphasis to the need for further short-term stimulus combined with tax increases and/or spending cuts later? Difficult to do, of course, but what is the objection in principle?