Argumentation is a truth-seeking interaction. Aggression is opposed to truth-seeking, it is unreason. Accepting reason is accepting the non-aggression principle. Someone engaging in unreason cannot coherently make any truth claims, so unreason cannot give rise to the negation of a proposition. You must therefore accept reason to argue. This means that the normative structure of argumentation implies non-aggression, which is dialectic proof of the NAP.1