His contention with jus soli from what I understand is that it creates a phenomenon which he terms "anchor babies", meaning INS is reluctant to deport illegals because they don't want to break up families. I have to agree with him. The Fourteenth Amendment (1868) wasn't ratified in light of the welfare state and the level of immigration we see today. It makes sense to rethink the idea of birthright citizenship. In fact, most other Western nations have a modified version of jus soli requiring either outright citizenship on behalf of the parent or at the very least the ability to claim residency for "x" number of years ("x" being the figure as determined by legislation).

As far as Libertarianism being against human nature, it's no more true than a Republic being for human nature. We have to be careful what we term "human nature". Just saying it doesn't make it so.