So there’s a reasonable argument for leaving the question of how to deal with future problems up to future politicians.
The point is that the case for urgent action now to reduce spending decades in the future is far weaker than conventional rhetoric might lead you to suspect.
So why are we messing around with this stuff? Why should we worry about the future? We're doing fine. Interest rates are rock bottom---we can borrow and spend till the cows come home. And surely "future politicians" will possess the will and integrity to make the tough decisions, just in case today's policies don't yield the economic bang for our buck Krugman anticipates, right? Hmm...
Of course you know Greece's past politicians would have none of that "conventional rhetoric" either.
I love it when a partisan hack professes credibility by citing "non partisan" groups when their projections jibe with his position (Krugman cites "the nonpartisan Center on Budget and Policy Priorities"). Essentially saying, "since I'm a partisan hack, and I don't deserve credibility, here's a credible source that supports my incredibleness."