I don't recall having previously heard of Kevin D. Williamson, and I have precisely one reason for thinking he is a scumbag. It is the first two sentences of his recent column:
It has long been rumored that Paul Krugman does not write the New York Times column that appears under his name. I have no reason to believe that that is true, but I hope it is.
Read more at: http://www.nationalreview.com/article/443696/deficits-matter-always-not-just-when-republicans-occupy-white-house
I can't think of any honest reason to repeat a scurrilous "rumor" that you don't believe is true. Can you?
In any case, the rumor seems absurd, since Krugman is a prolific and indeed almost compulsive writer. Also, Google doesn't seem to have heard of it.