Julian Sanchez says:
In response to immigration minimalists who worry about the stress influxes of poor immigrants put on social programs, libertarians are fond of responding that the problem, then, is with the programs and not the immigrants.
Yeah, but it's easier (though not easy) to fix the immigration problem than it is to roll back the welfare state.
Sanchez's comment and my response illustrate perfectly the difference between doctrinaire libertarianism and neolibertarianism.
(Thanks to Glen Whitman for the link to Sanchez's post.)