Free trade is often used to move work to countries without unions.

Not advocating either position here, just pointing this out.

Yes, so unions tend to kill countries where they're too strong. They tend to promote short-sighted action that save/retain existing jobs. This makes it harder for the economy to change when it is needed which in the long run leads to failed businesses, an uncompetitive work force and unemployment. Maybe unions is like democracy in that they totally suck, but the alternatives are worse. However, unions should definitely have their power checked.