> Krugman is a partisan hack that has a Nobel Prize is one very specific area of economics. It does not qualify him to opine on all other areas.
That seems to be a general feature of politically-engaged economists on both the left and right. I see Krugman as basically a mirror version of Milton Friedman: a blowhard whose statements on politics and policy preferences are usually wildly unsupported by empirical evidence, but who did also do some genuinely good economic work.
I read a piece on Krugman that was really interesting. For one, it challenged the exact perception that you're advocating: that Krugman takes strong stances on policy matters and uses strong language to defend them, to the detriment of the economics behind them. Interestingly, the piece pointed out that Krugman is usually the stereotypical economist -- quick to qualify and slow to make a strong policy statement without mountains of evidence. The writing style of Paul Krugman may be more the writing style of his wife, who encouraged him to advocate for more policy change. The article definitely painted Krugman's column as more of a cooperation between him and his wife than a straightforward economics work.
There is a very common fallacy committed by people outside economics in thinking that Krugman has something substantial to say in areas of economics outside of his very narrow focus of expertise. Let's say you founded a successful advertising-based Web startup from a scratch and you exited for 8 digits. People who are only vaguely familiar with technology and computers (let's say nurses, taxi drivers, high school teachers) will now think you are an expert in pretty much all matters related to starting a business and computers. However, unless you are a pompous egoist, you should realize that your opinions, even in seemingly very related matters, like running a Web store or creating an iPhone app, will likely be quite uninformed. Krugman's opinions are about economic matters much further away from his true area of expertise than your opinions about running a Web store.
That's a somewhat strange example to use on a site hosted by Paul Graham, who writes about a pretty broad set of things, not all of them very strictly tied to the things he's particularly famous for.
This is generally true of politically-engaged writers of any sort. Politics, at least popular politics (versus academic writing), is polarizing by definition. And generally the data isn't there to support any preference (or equally true... the data is there to support any preference).
This is why, I believe, that why someone supports a particular preference is almost as important as the preference. Although I should add figuring out why people have certain preferences is often difficult, since people are often not forthcoming with their underlying assumptions.
That seems to be a general feature of politically-engaged economists on both the left and right. I see Krugman as basically a mirror version of Milton Friedman: a blowhard whose statements on politics and policy preferences are usually wildly unsupported by empirical evidence, but who did also do some genuinely good economic work.