Greg Mankiw, whose work and insight I really admire, argues against protectionism of Obama government. However, he does make the popular point - that lower Chinese Yuan helps keep cost of US consumption basket lower. Henry Ford turned this argument on its head and increased wages of his labourers so that they can afford to buy the cars Ford made. In the same vein, I think Americans would be happy to afford higher cost products and buy them rather than have low cost products that they cannot afford. To make it clear, I am not denying the beneficial effects of lower cost products. Just that the real argument for free trade is different.
US needs to keep the roads to China well-paved. Sooner or later the Chinese Yuan will appreciate against the US dollar. Then US will need China to keep trade barriers lowers to allow US access to Chinese markets. But that means keeping US trade barriers down in current scenario. Obama talk on protectionism might only serve to precipitate the currency regime change. But even just talk will be harmful for US interest in the longer term. Obama will do well to take up Wen Jaibao's free trade argument.