One argument I often run into while defending an anarchist position is the blanket statement, "We need to apply the gospel to all spheres of life." Implicit in this claim is a naive acceptance of the validity of certain "spheres" which have become almost universally axiomatic.
But the "spheres" as we know them today did not always exist as such. William Cavenaugh has cleverly described the evolution of these social boundaries in this article. http://www.jesusradicals.com/library/cavanaugh/Wars_of_Religion.html
He shows that the modern conceptions of religious and political, private and public had a long and bloody history in their creation. Religion became privatized and the Church became the arena in which salvation referred to matters of the eternal soul, whereas the State became the public arena in which matters of social ethics were defended through a monopoly of lethal coercion. The conscientious Christian, then, would exercise his heavenly citizenship within his activities at church, and work to produce a more just society through participation in the activities of the State.
But there are quite a few problems with this arrangement. It implies that a just society is something that can be accomplished through fear of the sword, rather than solely through saving grace. This gives the State credit for something only Jesus can do through the power of the Holy Spirit. That is idolatry. It also prevents the Christian community from showing God's mercy to the mortally guilty, other than giving them hope for an afterlife. For instance, if a Christian sought to obey his Lord's command to love, feed and clothe an international criminal, it would be considered an act of treason by the State. Furthermore, any social reform could only be accomplished by playing to the autonomous rules of the secular playing field.
So to read Romans 13, for example, with these social "spheres" in mind, is to read it anachronistically. We need to recapture the political and public reality that the Church alone is the fullness of him who fills all in all. We are a complete alternative society.