You are going on his newspaper columns, which are idiotic enough. The Nobel Prize Committee evaluates what he has published in peer reviewed journals, which is very different. If you want to accuse Krugman of being schizophrenic, fine. Paul Krugman the populist columnist may be a nut case. Paul Krugman the professional economist is first rate, however.
Maybe, if you are speaking of long ago work, before unhinged rage became the man's most defining characteristic. The bile he has been unleashing for quite a while is wrapped around his status as an economist and about economic topics. Everybody is entitled to political opinion, especially in a science so intertwined politics and policy. But do you ever remember Friedman or Galbraith red faced while declaring their hatred for anybody? If you had do you think that may have discredited their work?