We view the original state of nature as pure freedom. These groups formed corporations to provide security to their customers in exchange for tribute - payment - which was given to their shareholders: the warriors or nobility. Doesn't history then prove that over the course of time a state of infinite competition settles into one of multiple monopolies which band together to stamp out potential challengers in their market? This entirely disproves libertarianism's main argument that infinite competition will provide infinite freedom.
That's not the main argument; the main argument is on ethics, claiming that using coercion is immoral, and the use of systematic coercion through the state is still systematically immoral.