Their arrogant little self-importance and self-indulgence prevents them from learning anything useful from history. And then there are those who are just too busy to care or just simply too lazy or stupid. They just need to create their own brand new shiny universe, together with their own brand new shiny lessons to learn from- if they ever do. It is what it is, that's life.
Fuck that.
Krugman is one of the brightest voices in the country. He isn't talking out his ass at all, he's saying that all the arguments against Keynesian economics are false (or v.v.) - and he's absolutely right. Every time someone tries to bring up a historical example of why he's wrong, he is ready with the answer for exactly how that situation is totally different. And his answers include hard analysis of the economics of the time, not just shouting like you hear on the right (because they're wrong and have nothing else left to do). The same applies to arguments in principle - he has totally sound arguments to support what he says.
It's arrogance to call that arrogance, because it's absolutely true: the ONLY way out of this mess without waiting for years and years is Keynesian.
If you have real arguments with what he's saying then fine. You'll be wrong, but at least we'll have a discussion. But saying Krugman is a fool is an indication of the poster's lack of understanding, not anything about Krugman.
And by the way, it's not like he's some lone lunatic out on the fringes. There's no shortage of other economists who say the same thing - and the reason is that it's reality. They may disagree about some things, for example Jamie Galbraith argues that the government could simply write checks to people, preferably to do something useful; the only difference if they issue a bond to cover it is that the banks make some interest. Krugman disagrees with that, because eventually - and not now! - it will lead to inflation. But they both understand that the government needs to spend money to create jobs right now, since monetary policy has reached its limit.
And Knife is an idiot in any case. The sum total of his arguments is that Krugman has an agenda and invents facts. Not only is that moronic, saying that is the exact definition of a stupid asshole.