Gary Galles is right that Herbert Spencer was right that protectionism is aggression-ism (although I don’t agree with Prof. Galles that Smoot-Hawley, despite its many faults, was a major cause of the Great Depression). A slice:
However, protectionism cannot protect all. It provides special treatment for the politically favored at the expense of others’ rights and well-being. In fact, it harms all American consumers not given special protection by removing options their choices demonstrated were preferable to them. The harm to preferred foreign suppliers is also important, and not just to foreigners. Their reduced earnings due to the protectionism will harm other American producers and workers by reducing overseas demand for their products.
Going beyond the protection of our common rights, protectionism cannot benefit all. It restricts choices and competition, crowding out mutually beneficial arrangements for all but a favored few. It means that most of us “win” less than before, not more, and leaves unanswered the question of why some should receive government imposed coercive charity from the rest of us.