What is really odd about the statement is that Krugman is one of a handful of economists who think trade protectionism is a good idea. We might soon get to test these theories as Trump is all about trade protectionism.
No, he's not. He has occasionally made the point that certain arguments against protectionism are misstated, but AFAICT consistently does so alongside saying that protectionism remains harmful, a time a minimum because it reduces efficiency and aggregate output. [0]
[0] e.g., http://mobile.nytimes.com/blogs/krugman/2016/03/04/the-mitt-...