Most of the article is just a calumnious personal attack on an ever-growing enemies list, which now includes "new Keyenesians" such as Olivier Blanchard and Greg Mankiw. Rather than source professional writing, he plays gotcha with out-of-context second-hand quotes from media interviews. He makes stuff up, boldly putting words in people's mouths that run contrary to their written opinions. Even this isn't enough: he adds cartoons to try to make his "enemies" look silly, and puts them in false and embarrassing situations. He accuses us of adopting ideas for pay, selling out for "sabbaticals at the Hoover institution" and fat "Wall street paychecks." It sounds a bit paranoid.
Klein offers survey data to refute Krugman's claim that Keynesians were "marginalized."
I remain sympathetic to Krugman's complaint about the sterility of macroeconomics over the past 30 years. However, I do think that by using the New York Times as his outlet, he mounted an academic assault from a fortress where his opponents have no chance of firing back at him. If instead he had made his point in an academic journal, then (a) he would have been forced by an editor to adjust the ratio of his rhetoric to his evidence base and (b) had to content with equal-time responses from those he attacked.