Both economic evidence and theory strongly support the conclusion that free trade increases the economic well being of all participants. Much of the increase in wealth in the post WWII era and the post-Cold War period, in particular, were strongly tied to the protocols of free trade. There will certainly be people and industries that are dislocated by the discipline of economic competition. In aggregate, however, wealth is increased and resources are more efficiently utilized. However, economic efficiency and welfare are not the only values against which public policies ought to be weighed.
Free trade is more an expedient than an ultimate value.
Domestic labor organizations argue against free trade citing the lack of worker protection in foreign countries, but many times such arguments are motivated less by a concern for foreign workers and more by a fear of competition from poorer people willing to work for less. The AFL-CIO does not spend much political effort fighting for workers' rights in the Sudan. Sudanese workers are not a competitive threat to American workers. Some argue that trade should be used as a lever to compel compliance with US standards. While there is merit in this concern, it must be balanced by the consideration that different countries in different stages of development might reasonably strike a different balance between economic growth and environmental concerns.