Martha Gill has a good piece on immigration on the Telegraph Blogs site today, pointing out the simple fact that people often forget: the main reason immigration is such a good thing is that it's really, really good for immigrants.
Sure, immigrants make the rich countries they arrive at richer and subsidise those countries' welfare states, but people in rich countries have a lot already. It's people coming from places like Somalia and Sierra Leone that have the most to gain from being able to work in the UK.
Michael Clemens's study, "Trillion dollar bills on the sidewalk", looks at estimates of the global GDP gains that would come from open borders. The gains range between 67% and 122%, depending on how many people actually migrated. Those benefits would overwhelmingly accrue to the world's poorest people, and that's a good thing.
Gill's piece is directed at the left, which is fair enough given that most defenders of immigration are on the left. But no side owns cosmopolitanism. Almost everyone has heard the slogan "trade, not aid" from people on the political right. They (correctly) see international trade as a much better way to improve the lives of people in poor countries than development aid. They want free trade because it works for poor people around the world, not just because it would also happen to make us a little bit richer.
It doesn't seem out of the question that the same kind of altruism might eventually spread to the right's view of immigration. That might seem unlikely, but the political right was once a bastion of protectionism, and that changed.
Fundamentally, immigration restrictions are laws that ban firms from employing certain people and landlords from renting or selling their property to certain people. What's right-wing about that?