Maybe Donald Trump is such a powerful communicator and pot-stirrer that other countries, embarrassed by their own trade barriers, will eliminate them. Then I will thank the president for the wonderful thing he did. Genuine free trade will be a recipe for wonderful economic growth. But I fear the opposite: a trade war and stagnation -- because much of what Trump and his followers say is economically absurd. "(If) you don't have steel, you don't have a country!" announced the president. Lots of things are essential to America -- and international trade is the best way to make sure we...