Hart provides an unusually astute observation:
This is a key difference between paleo- and neo-Calvinists (not to mention other Presbyterian transformers of cutlure [sic]). In the case of old Calvinism, the aim was to reform the church, which in turn led to various forms of political resistance and activism in order to worship God truly. In the case of new Calvinism, distinct marks of Reformed worship and polity are sacrificed in order to work with other Christians for the sake of a righteous and just society.Hart is mostly right. While we would insist that our worship and polity be Biblical (rather than "Reformed" for the sake of the label), those points (especially the opposition to idolatry) must drive the renewal of society by the Gospel.
The fruit of a just society flows from the tree of a society that walks and worships rightly before God. Reform the tree, and the fruit will be reformed. Sacrifice the tree for short-term political gains, and the fruit will follow the corruption of the tree. This is the historically reformed view of two kingdoms, as distinct from the Lutheran view that is mentioned in the quotation Hart thoughtfully provides.