Would there not have been due process before the American who joined Hitler was deemed expendable? No doubt there would have been due process, though it likely would also have been swift and sure in its finalization.
What worries us most is that the current administration view half the country as potential domestic terrorists. With the implementation of indefinite detention and drone strikes without due process, we need to worry. Would the government lock up whole segments of our society? Just ask the Japanese who were dispossessed of all but their lives during World War II. Would the government turn its drones loose on Americans within our borders? Just a look what happened at Waco and Ruby Ridge.