I rarely write a column that receives more criticism from my conservative readers than from my liberal ones. And it is even rarer when the column in question approaches a topic from what is supposed to be a “conservative” perspective, as it usually does. Yet this is precisely what happened recently when I wrote a column titled “Memo to the Democrats: We Need Free Trade with China.” It targeted the leading anti-trade voices in the Democratic Party, particularly Hillary Clinton and Barack Obama, and continued by explaining why free trade with China does indeed benefit the United States, at least...