Employers don't just think in terms of "person X meets our quality bar, and therefore deserves our standard pay - irrespective of geography". They think in terms of "return on investment" - how much it costs to hire X and how much benefit they get out of it. That's exactly what we want if we live in poor economy and are hoping to increase employment opportunities. Opposition to voluntary / free trade takes away such opportunities - especially from people who need it the most.