As an aside, the relative absence of that kind of movement in libertarian thought experiments has always bemused me; I think there's a somewhat utopian "everything gets better when you take the state out of the equation" notion at play. Everything doesn't automatically get worse, but it doesn't automatically get better, either. If the society still has discrimination, prejudice, and unequal justice, it's still going to face pressures to reform; most of us would rather see where we live be made "better" in our understanding of the term than be forced to move somewhere else to find that "better," even assuming we have the resources to make such a move.