Arguing for the "legitimacy" of the State (or government) with an anarchist-- using legal definitions and statist concepts-- is as pointless as threatening atheists with Hell for not believing.
It's just not going to work.
You are speaking gibberish while trying to defend the indefensible to someone who doesn't believe in the things you put your faith in.
And even bothering to respond, as an anarchist, to the statist making the "argument" is probably a waste of time.