There is a different strand of criticism of Krugman (and the neo-Keynesians in general) that is quite apart from his politics. At some level, this is a criticism of the modern economic profession itself, and its worship of mathematical models. This is conceptually analogous to but quite distinct from the Wall Street addiction to quantitative/stochastic modeling, which is behind much of the present mess. Krugman represents the pinnacle of that mathematical tradition. To be fair, Milton Friedman, ideologically the polar opposite of Krugman, has also faced similar criticism.