The free trade argument is based on the economic theory of comparative advantage. This just ends up being a measure of which market can be most effectively exploited for gain from every smaller nation a country like the US trades with.

These smaller countries end up producing a disproportionate amount of a small category of goods. Efficiency is good right? Well, it is until there's some form of economic disruption or downturn that suddenly lowers demand for that good. Then suddenly all the other things the country doesn't focus on are extremely expensive as the local currency devalues and they can't afford food and other core goods which they don't produce enough of. Hey, good news though, now their labor is even cheaper and we can have them work for pennies making something else so they don't starve.

Fair trade means the government doesn't interfere and tax things, it's the same thing as free trade. It's a really great system. For billionaires who own companies and would love to own slaves if they could. This is the next best thing though.