Postliberal "Red Letter Christians" and those in the emerging church preaching a repainted social gospel of a reimagined liberation theology can learn much in this sermon from Dr. John MacArthur:

One of the responsibilities that a preacher has is to bring the word of God to bear upon the church and the world, and to give God a voice to clarify and discern issues. So on the one hand, we are called to the exposition of scripture, explaining the Bible verse by verse, book by book. But on the other hand as well, we are called to address the issues of our time that affect us and to bring the truth of God to bear upon our understanding…

Without any lack of clarity, without any argument, therein lies the mandate for the Christian in the world: The ministry of reconciliation to God through Christ, which brings about righteousness, transformation, and a new creation. There is, however, today in Christianity, in its evangelical element, an emphasis on another kind of effort. It is an effort to produce morality…

And what I attempted to say in [the book "Why Government Can't Save You"] was if you’re dealing with the issue of salvation, the government won’t help. What I was really trying to say and what I did say in the book was that for Christians, the mandate is not about some kind of cultural morality. The mandate is about salvation. And the government plays no role…

And in a related issue here is the link to a message by Phil Johnson that "addresses the controversy that exists between the ministry of Dr. John MacArthur and that of Dr. James Dobson (Focus on the Family), on the issue of preaching the gospel to change the wickedness of man versus using political legislation to accomplish that end."