I don't quite understand what you mean here by the state being involuntary and anarchism being voluntary. If you point is that the minority would walk away somewhere if they disagree with the majority, I don't think this relocation will be by their free will and accord. Actually, they will be coerced to do so by the majority. It happens daily in life even without state and its laws. But exactly the introduction of state in the form of the law allows to break this otherwise circular argument...

Coercion
Threat of kidnapping, extortion, force or violence to be performed immediately or in the future