China is Subsidizing America's Standard of Living

Gary Becker does a good job summarizing the argument against trying to convince China to let the yuan fall against the dollar. Basically it goes like this: We want to buy Chinese goods, but Chinese goods can only be purchased with Chinese currency, so we give dollars to the Chinese central bank in exchange for yuan. But the Chinese government has this policy where they always give us more yuan than our dollars are really worth. So it's a good deal for us, and a bad deal for them. Why do they do that?

Even more relevant to Americans is the question, why is Obama trying to convince the Chinese to STOP doing that?

The comments on Becker's blog aren't working, but here's what I tried to post in reply:

Can it really be sheer foolishness on the parts of both the Chinese and American governments? What can their respective motives be? 

In America there has been a long term advertising campaign against any trade deficit, and many American voters have been persuaded to embrace a cause (make imports more expensive) that is likely not in their own interest. Have unions and export businesses so completely captured trade policy in the US? 

Is there a similar explanation for the Chinese policy?