ZPG and Immigration
There are, perhaps, good reasons to limit immigration. Malthusian population-control is not one of them, as Linda Chavez notes in Fixing immigration:

I wonder how many conservatives who embrace the anti-immigrant message know that their fellow travelers' roots are in the pro-abortion, population-control movement.

Dr. John Tanton, who was the brainchild behind many of the most prominent restrictionist groups, including the Federation for American Immigration Reform, the Center for Immigration Studies and Numbers USA, is a past president of Zero Population Growth. These groups often cite demographer Leon Bouvier's work to support their arguments. In his book "How Many Americans?: Population, Immigration and the Environment," Bouvier and co-author Lindsey Grant advocated reducing the American population to 150 million by the end of this century -- that's almost half the current population. Although they're guarded in suggesting any draconian measures to achieve this goal, averring that "Deliberate reductions in life expectancy to reduce population are, of course, out of the question," their prescriptions are nonetheless chilling.

"To begin with," they say, "it would be pointless to assume that American women will altruistically decide to have but one child for the good of the society." So they favor government policies that will achieve that end. "All proposed legislation, regardless of specific intent, should be evaluated as to its possible impact on fertility," they argue. And, of course, they support additional government-funded research for more effective contraceptives and better access to abortion. The book was written during the Clinton years, which accounts for this gem: "[T]here is hope that with the end of the Reagan-Bush era, a more enlightened executive will see the advantages of at least limiting, if not stopping, population growth."

Make no mistake, these folks are after immigrants now, but they want into the bedrooms of American citizens next. Unlike some racist elements in the anti-immigrant movement (they exist, as I can attest from the racist diatribes I receive every time I write on this issue), these people object to virtually all immigrants, but dislike Hispanic immigrants more because they have higher fertility rates.