In my view, the only valid argument against the anarchist position is the one David Friedman called “the hard problem,” i.e. the question of whether a stateless territory could potentially defend itself against external invasions by states. All the other arguments are merely special pleading on behalf of various political, cultural, or economic special interests, or based on a misunderstanding of the anarchist position. While I have certain disagreements with the speakers in this video, this is a great discussion.
Read a Ph.D. dissertation on the military defense of an anarchist society here.