Free trade was more free in the 19th century. We have much less globalization now than we did then.
Free trade is not fully realizable politically because it's only in the general interest and in no one's special interest.
Free trade hastens the social revolution. It is in this revolutionary sense alone, we should vote in favor of free trade.
Free trade is based on the idea that the state must refrain from 'interfering' with the economic activities of self-interested citizens and instead use its power to guarantee open economic exchange. (harvey brief history of neoliberalism).
Free trade is a win-win situation for all trading partners involved and should not be interfered in because it allowed each country to specialize in the production of those commodities for which it had a comparative advantage.