As to why I think libertarians are nuts to favor mass uncontrolled immigration from the third world: I think they are nuts because their enthusiasm on this matter is suicidal to their cause. Their ideological passion is blinding them to a rather obvious fact: that libertarianism is a peculiarly American doctrine, with very little appeal to the huddled masses of the third world. If libertarianism implies mass third-world immigration, then it is self-destroying. Libertarianism is simply not attractive either to illiterate peasants from mercantilist Latin American states, or to East Asians with traditions of imperial-bureaucratic paternalism, or to the products of Middle Eastern Muslim theocracies.
There are a number of responses a libertarian might make to that. Not included in those responses, I think, given the current state of our national affairs, is the argument that Providence has inscribed a yearning for liberty on every human heart.
A libertarian might, though, say that while libertarianism could indeed be a hard sell to immigrants from very illiberal political traditions, it will appeal to their Americanized children, to the second generation. Possibly so. Even setting aside the great strengthening of the welfare state caused by the preferences of that first generation, though, to sell libertarianism to the second generation would need a tremendous missionary effort. According to Brink Lindsey, only 13 percent of Americans currently lean libertarian. If decades of libertarian proselytizing have only achieved that much success with a population rooted in the traditions of Pericles and Magna Carta, of the Renaissance, Reformation, and Enlightenment, of Washington, Jefferson, and Madison, how well should libertarians expect to do with the political descendants of emperors and caliphs, of Toussaint L’Ouverture  and Mao Tse-tung? ~John Derbyshire 
This all makes a good deal of sense, and I have written  very  similar things  on related matters  touching on the almost inexplicable urge of many libertarians for open borders and mass immigration. This blind spot to the negative consequences of mass immigration for their own political vision of smaller government and free individuals is part of what I repeatedly refer to as “The Libertarian Matrix.” As in the movie of the same name, libertarians carry on without realising that they are trapped in the reality-distorting bubble of their ideological assumptions. It is entirely fitting that a group dedicated to “free minds” should have such difficulty freeing their own minds from this prison of wrong assumptions.
In addition to being a guaranteed cause of libertarianism’s extinction or even greater marginalisation (were such a thing possible), libertarian enthusiasm for mass immigration ensures steadily increasing hostility to libertarianism from, well, people like me and a great many other Americans who will begin telling the liberts what they can do with their “moral right of exchange.”
Missionary effort or no, the possibility of second or third generation children of immigrants from illiberal political cultures embracing libertarianism is one of those nice, preposterous ideas, sort of like the hope that bringing in millions of nominally Catholic Mexicans will help shore up the conservative side in the culture wars (this is true if we are referring to the Mexican conservative side of those wars). The latter is based in quaint, romantic notions about pious and traditional Mexican villagers from stable and intact families most recently seen in The Three Amigos. But this is at least a claim that makes some nod towards a romanticised image of another culture. This gets the reality of the culture of the immigrants wrong, but at least it takes that culture seriously one way or the other. Libertarians will tell you until they are blue in the face and you are quite sick of hearing it that the political culture of the countries whence these immigrants come is basically irrelevant. Immigrants are hard-working and entrepreneurial people who are trying to get out from under the dead weight of restrictive economic and political arrangements back home–they are therefore supposedly natural libertarians (when they get done being natural conservatives, of course–they work a double shift, as befits hard-working immigrants). But this is to go against every shred of empirical evidence we have for all major waves of immigration. People reproduce the political and cultural habits with which they are raised; they often do this without giving it much thought, because this is “the way things have been done” as far as they know. These habits are their framework for operating in the world, and they do not abandon them unless they are given good reasons to do so. In addition to which, with the exception of very unusual ethnic communities (Cubans, Vietnamese) that tend to identify more with Republicans out of decades-long resentment at Democratic betrayals of their home countries, ethnic immigrants are solidly reliable blocs for the Democrats as constituencies for expanded government services and greater government activism.
Always have been, always will be. This affiliation continues into second, third and later generations. It has taken tremendous efforts on the part of Democrats to lose their natural advantage with their old ethnic white constituencies, and even here they have not lost all of them by a long shot.
Expanding government services is what these people have come to expect from government in their home countries (or it is the sort of thing that they pushed for back home without success, which is why they left and came here), and it is what many constituencies in a mass democracy expect in any case. Many would also see support for these policies very much in pragmatic, self-interested terms (libertarians would be so proud!) as a way of getting services and support that their communities, as communities that are still fairly new to the country, might well “need” more than others. Anyone interested in rolling back government, encouraging individual independence, supporting market solutions and generally decreasing the role of the state in all aspects of life obviously does not want poor PRD and PRI voters moving to the United States in large numbers. It is especially the large numbers that are the important factor here, but any number would be that many more people inclined to oppose anything remotely resembling libertarianism. This is still one more reason why there will be no liberal-libertarian alliance of any meaningful kind, and why the idea of the Libertarian Democrat is a bad joke. If the libertarians would like their ideology to survive and possibly even grow in influence, their major spokesmen and organisations would drop all of this pro-immigration chatter once and for all. But, as we already know, that isn’t going to happen.