Animal rights, mentioned below, is only one of many areas where rights-theory fails to work. Another example is that of incompetent, irrational, or non-adult humans. Hitting people, we think, is wrong because it violates a right not-to-be-hit. Your right to swing your fist ends, etc. etc. But what of corporal punishment? Is that not "aggression"? Personally I think it is OK, suitably governed, but I'm surely aware that others disagree on that. Philosophically, I can tolerate error: anarchists tend to be localist. The only place I am concerned with the legality of corporal punishment is where I happen to live. But the statist cannot be philosophically tolerant.
If a statist really has no opinion on an issue, then the fight over it by others more idealist doesn't really concern him, but he will get one policy or the other as a result.
The tolerant statist with an opinion is always hit with an argument from ideals. If something is right for him, in an idealist world it must be right for everyone. And if that's true, then a Federalist argument - to let other sub-states determine a different policy - looks either wrong, or like moral cowardice. Why not use the Federal state to crush the incorrect policies?
To an anarchist idealist, things look different. "Crushing" other people's laws is tantamount to war. So ideals, even if attractive, must be worth fighting a war over. The practical result will be a lot fewer universal laws in anarchy, and a lot greater variety.