(If we ignore the fact that both sides benefit from the free trade)<p>The central tenet of the rightist ideology is free market and free trade. That one is obvious.<p>The central tenet of the leftist ideology is wealth redistribution, that the rich should compensate for the poor. Thus, given that the Americans are orders of magnitude richer than Chinese, it is only fair that some of the wealth of Americans be redistributed to the Chinese. The international trade involve altruism for the same reason that the aristocrats altruistically share their (previous) privilege with the plebeians.