In the language of economics, human well-being is affected not only by the mean (the prosperity of the average citizen) but also by the variance (the increasing dispersion between rich and poor). In plainer English, the incentives and equal opportunity afforded by free trade simultaneously improve the overall welfare of mankind and increase socially corrosive disparities of wealth. Even if trade slightly improves the real income of those at the bottom, they will feel the pain of economic deprivation when they fix their gaze at the growing wealth of those above them.
