An article by the Capital Research Center points out how labor union's protectionist arguments are not so much about protecting jobs as about protecting their power. Witness how they oppose free trade even with European countries with greater labor market restrictions than in the U.S. Hard to argue that would lead to a race to the bottom.
Protectionism looks even more silly in light of the GAO's finding that in 2003 relocation of jobs overseas accounted for 13,000 or 0.9 percent of the 1.5 million layoffs that occurred. Hardly a "giant sucking sound." More like statistical noise.