It's also interesting to note that some Greens on the European left are against open borders and support immigration moderation. One of the most notable articles is from Colin Hines in the United Kingdom: Progressive Protectionism - the Green Case for Controlling our Borders.
Meanwhile in the USA I continue my battle against left-wing supporters of open borders: Here is a link to the email letter that I wrote to New York Magazine in response to its recent article supporting open borders written by Eric Levitz: Click Here.
I remind my fellow lefties that throughout the democracies of the world, most citizens support moderate immigration, not open borders. This is shown by the recent survey by PEW: Many worldwide oppose more migration - both into and out of their countries. I also remind my opponents that they are clearly on the losing side of history, so why don't we all work together for reasonable and moderate immigration policies for the Western Democracies to help stop the increase of right-wing populist movements and work together on a worldwide plan to help the more desperate countries of the world so that their citizens won't feel the need to migrate to our countries.
Editor's Update 1/24/2019: This article by David Goodhart, Why the left is wrong about immigration, written nearly six years ago, is even more relevant today and explains why the left should be against open borders.
Editor's Update 10/20/2021: This article by Joseph Chamie, Mind the Gap: Public and Government Views on Migration Diverge (pdf), written over 10 years ago, explains why it's critical for mainstream political parties which tend to favor larger immigration, to take into account majority public views which tend to favor immigration moderation, in order to avoid disastrous political outcomes. He sure hit that nail on the head!