In everyday life, people sometimes think of competition as something that takes place between buyers and sellers–the buyer wants a low price and the seller wants a high price. They seem to be in conflict. But the real competition is among the sellers who compete to get the business of the buyers. So Safeway and Giants and Wegman’s are competing to attract me into their store and buy their stuff. I get along pretty well with my grocery store.
Similarly, in the market for ideas, it looks like Krugman is competing with Taylor and Sumner and others to provide the best explanation of the state of the economy. But equally and maybe more important is that Krugman is competing with Delong and other interventionists in appealing to people who already favor intervention and who read the New York Times. The same thing happens among less interventionist economists. That is part of the reason that on his blog and in his column Krugman spends less time educating and more time cheerleading. He cheers up his side  about its virtues and makes them feel superior to their opponents. He is a heckuva cheerleader. But I wish he were more of a teacher.