His argument was basically this: in America, we may despise the idea of working in a sweatshop, but a person who is desperately poor prefers a hot factory and long hours to starving in a slum. Given this, Kristof says that well-intentioned demands by the (soon to be) Obama Administration for stricter labor standards in free trade agreements (e.g. the US-Columbia free trade agreement) are really hindering development in struggling countries and depriving the poorest in the world of opportunity to lift themselves out of poverty. If a company has to meet high standards in one country, then they'll simply go to the neighboring country that does not have the standards.
Fair enough. Opportunities for employment are relative depending on where you stand. Just as Nicholas admits that he would not want a job in a sweatshop, neither would I. But just because desperation would drive some in Cambodia to view a sweatshop as an "improvement", this does not mean that we --who consume cheap products -- must accept their working in quasi-slavery conditions. There is a grey area between ultra-strict labor standards -- like providing full health care, paying far above market price for labor, and short work days -- and no labor rights. Things are relative, but there is also a baseline that we must establish as human beings.
The International Labor Organization, which is sensitive to labor relativity everywhere, espouses four widely ratified fundamental human rights: the right to collective bargaining, freedom from forced labor, freedom from discrimination, and the restriction of child labor. This is the minimal amount that we could ask. In a sweatshop, workers are regularly deprived of these simple rights. Much of modern slavery finds its home in these hell holes.
The distinction here is between a "sweatshop" and a "labor-intensive factory". Both are places that few in the US or the developed world would want to work, but the latter recognizes the humanity of its workers, while the former does not. Just because we -- in the developed world -- were fortunate enough to born in the US, EU, or Japan, this does not mean that we should expect others with less luck to accept a "step up" from a garbage heap to a labor prison. This is a false choice.
Free trade is good for the whole, but it need not punish individuals.