The very ferocity and coordinated nature of the attacks on Sanders makes clear that the Democratic establishment views Sanders not merely as an annoyance, but as an existential threat. And he may be, at that.
New York Times columnist Paul Krugman is an effective polemicist with a wide readership. So when he makes arguments that are at best factually wrong and at worst disingenuous, one cannot simply ignore them.
Listen to any conservative talk show host and they'll regularly remind their audience that the Republicans are the party of ideas and that their books consistently top the best-seller charts. But for some undiagnosed reason they've managed to win only two of the past six presidential elections.