Over at Internet Commentator, Frank McGahon writes:

From the point of view of the rest of society there's nothing wrong with "poor academic and economic performance" per se [since] the costs of such "poor" performance are borne by the actual "performers."

Though this debate started with Frank, I am not trying to single him out--this sort of argument seems common amongst loose and open borders libertarians, when they'll even admit that many immigrant groups aren't doing well economically or academically.

The problem with the "libertarian" argument in favor of loose/open borders is that, even in the absence of a welfare state (unlikely to ever happen), and the absence of government-funded infrastructure (even more unlikely to ever happen*), there are certain costs of poor-performing, high-crime groups that are unavoidable. Unless one plans to hole himself up on his own private property forever**, one will always have some exposure to his fellow citizens, including those who are poor, uneducated, and more likely to commit violent crimes. Thus, the only practical way for people to express their preferences as to the economic and academic characteristics of their new fellow citizens is through the government. I am certainly not questioning the idea of private property, but I *am* questioning the idea of abolishing public property. The average person's control over his circumstances should not be limited to a 1000 square foot house. A middle or even lower-middle class person should be able to choose to be insulated from crime and poverty without excessive cost. Under mass low-skill immigration, this is increasingly not an option; thus, one's freedom in a country that allows low-skill immigration is reduced, even free of welfare and infrastructure costs (which is, as I said before, highly unlikely to ever happen in an industrialized country).

*Even many small government conservatives and libertarians do not necessarily find such a situation desirable; in fact, I am not sure fully privatized transporation and education are good ideas. A private justice system is almost certainly a bad idea.
**Assuming one can afford a property far away from poverty and crime, which will become more difficult as the U.S. and Europe accept more poor/unskilled/uneducated immigrants