When thinking about the relative merits of protectionism, I always reflect back to the two world wars. In the first world war, you have the tragic scene of socialist parties voting for war in defense of the nation and against international worker's solidarity. Before the second during the Depression, you see nations - and empires - descending into a spiraling escalation of trade barriers, ostensibly to protect national industries and (workers' wages I would guess). Neither had a happy ending for the workers of the world.
The emphasis should be on bringing foreign workers' working conditions up, not on defending native working conditions no matter the cost. The propagandists for corporate America love to define the debate as one between their version of free trade and the jingoistic protectionism and isolationism of Pat Buchanan. If they want to make the world one economy, then it will truly become one society and we'll have the beast in plain sight - one enemy to deal with, as it were.
Here's a conservative Englishman who's against joining Europe: "After years when the opponents of the cultural revolution have fought their little isolated skirmishes and lost them, here at last is a full-scale battle against a recognisable threat to our entire way of life. It is as if the conservative elements in society have been hacking at a fogbank with blunt cutlasses, to all appearances attacking an imagined foe. Suddenly the fog lifts, and the great scaly monster of national abolition is revealed in all its ugly menace.'"
If they succeed in making the world one economy and one society, the fog will lift and the great scaly monster of Capital will be revealed in all its ugly menace.