This is the basic class-envy lie that is at the heart of the argument. It is complete and utter nonsense, based upon the thought of what middle class people would do if they were rich. Just who is it that supplies the bulk of charitable dollars? Taking from the rich only results in more pain for the poor.
The rich do more purchasing than any 20 members of the middle class. They replace cars and homes more often on average, and are responsible for many jobs involving imports that the middle class could never support. The rich also purchase higher margin items, which support lower prices on other items for middle class consumers. For example; airlines would be charging a much higher average price for seats, if not for the offset margin for Business and First class seats. Is that what we want?
It is a cliche to ask, but how many people got their last job from a poor person? Everyone knows that if you raise the minimum wage, you increase unemployment, because business costs are always passed down to the consumer. By restricting trade, you essentially do the same thing. Lower COGS(costs of goods and services) allow companies to ultimatly either employ more people, or avoid employing fewer people. If anyone thinks that repealing NAFTA will do anything to improve employment levels, I have a bridge to sell them.
A good example would be Boeing; who may be building their new 7E7 aircraft from an entirely new company/conglomerate with Airlines owning an equity share. Who is to say that if they are unable to get the cost/tax structure needed to turn a profit, that this company will be based in the US? Boeing could build their new plane completely on foreign soil, and there would be nothing anyone could do about it.
NAFTA conserves more jobs then are lost, and the class-envy argument is specious.
All third world countries have a rich class and a very large poor class. How come all that purchasing power they have in countries like Haiti and Mexico ---where there are actually plenty of rich --as many as anywhere, are doing so poorly? It's the middle class and only the middle class that matters. Without the middle class we're like any other third world hole.
What you need to worry about is what the ex-middle class people will do when they're poor, when they have nothing to lose. Look in history books at what brings on a revolution --an overthrow of power. Look at the French Revolution --- they haven't had one since they've had a middle class. Angry peasants aren't good to have around.