All they see is jobs being lost in Detroit. They do not see the jobs that are being created in countless other industries because free trade allows consumer resources to flow to the areas they deem to be of highest value to them. Studies done by the Institute for International Economics and others have found that protecting a domestic industry by raising a tariff, implementing a quota, or having a voluntary restraint agreement with some country actually destroys more jobs than it saves. Although some tariff or quota might save 20,000 jobs in the auto industry, it also destroys 30,000 or 40,000 jobs in other industries, or prevents them from coming into existence. Protectionist policies do not enhance social harmony, they reduce it.
Free trade does just the opposite.
It allows consumers to buy the products of their choice at whatever price they can find in the international marketplace. The spread of trade results in a higher standard of living for the vast majority of the population. As individuals become more familiar with the products of other countries, they tend, over time, to change their opinions of foreigners. Rather than think that their country's products should be supported at any cost, they begin to hold the view that the origin of a product is not as important as its quality and price. Thus, nationalistic ideas and provincialism take a back seat to rational self-interest.