Premise: Initiating violence against entire categories of people is justified if the end result is more overall freedom.
That is the “ends justify the means” bullshit excuse that “closed border” advocates pretending to be anarchists constantly use. “Letting in more statists would cause less freedom, and therefore initiating violence against millions of people who I don’t know, and who haven’t actually done anything yet, is justified!”
Aside from being immoral and statist, such a “principle” could also be used to literally justify mass murder. “Well those people don’t care about freedom, so if we kill them all, the world will be more free overall! If we just exterminate everyone who doesn’t believe what I believe, then we can have utopia!” (And I’ve heard “alt-right” fascists saying pretty much that.)
This is why I wouldn’t trust a “closed border” “anarchist” as far as I could throw them: they’ve already demonstrated that they will abandon principles, and cheer for violent aggression, if they think it would serve their own interests to do so.