Free trade (and free immigration, which is essentially the same) is undoubtedly good on the whole. However, the current anti-trade pandering from Trump / Sanders and the like may also be correct.
Expanded access to markets may be unequal. For example, if there was an untapped country that had a million unemployed meteorologists - signing a free-trade deal with that country would most likely be terrible for meteorologists in America - although all other Americans would be better off with improved weather forecasts.
Replace "meteorologists" with "factory laborer" and you can see why so many of the current anti-trade folks are upset with what they see happening. They aren't barbers or plumbers - they're factory workers. The barbers, plumbers and engineers get cheaper stuff (and are better off), but the factory workers get paid less.
Expanded access to markets may be unequal. For example, if there was an untapped country that had a million unemployed meteorologists - signing a free-trade deal with that country would most likely be terrible for meteorologists in America - although all other Americans would be better off with improved weather forecasts.
Replace "meteorologists" with "factory laborer" and you can see why so many of the current anti-trade folks are upset with what they see happening. They aren't barbers or plumbers - they're factory workers. The barbers, plumbers and engineers get cheaper stuff (and are better off), but the factory workers get paid less.