I don't think there's any need to suggest Krugman is stupid based on this.
He is a thoughtful man and a recipient of a Nobel prize for economics, you might disagree with him and think his theories are dead wrong- but being wrong is different to being an unsophisticated thinker. Let's be mature about this.
Like most neo-keynesians he has repeatable gaps in his own logic and when win he can't win a debate by pissing off the opposing side he decides to act snide and patronising instead, that is unsophisticated thinking at its finest, in fact, sounds a lot like the way a religious person acts I think.