Most market anarchists argue that states are coercively-imposed territorial monopolies for the provision of defense and dispute resolution services. More plainly, they are protection rackets with good PR.
The most basic function of any state is to protect the lives of its citizens. However, individuals are not given the ability to choose who they will have protect them. They are forced to purchase this protection from their local monopoly who will take their money for the service whether the individual wants it to or not. If they resist, they will be jailed or worse.
One of the ways market anarchists approach this issue is to ask, “should a service ever be forced upon someone at gunpoint?” We, of course, oppose such acts of brutality on ethical grounds and also assert that such forcible interference with consumer choice creates horrible incentive problems. Why should a state treat you nicely if they can get away with not treating you nicely?
A state is not governance based upon the consent of the governed, but conquest under a false pretense of legitimacy.