Krugman's points are superficially ok, but his reasoning strikes me as beside the point -- the point is not that paranoids are running our government.
The point is that those who run our government manipulate the public using the paranoid style.
Krugman ignores Tom Frank's terribly valuable point about all this: these people in power don't believe the stuff they sell. Even Tucker Carlson has said that as a guest on Hard Ball.
To ignore this is to validate the debate on wedge issues. To do that validates the failed political strategy of the Democrats over the last decade and more.
Thus, Krugman may be simply pandering to the choir.
Maybe he lost the ball in the lights. Maybe he does not know how to address the real issue. Maybe he is part of that vast Democratic "conspiracy" that inexplicably fails to disengage from these games.