Throughout the history of Christendom, whenever society has turned away from perceived Christian principles, (those of the denomination in power at the time), the church has turned to government coercion to force people to act according to said principles. This is where we are in America right now. Christian conservatives (chriscons) see sky-rocketing out-of-wedlock birth rates, gay marriage, abortion, and all manner of societal ills as evidence (sound evidence) that society is no longer bound by Christian principles. And now these chriscons are looking for the government to step in and force people to live by biblical law.
As a Christian Libertarian, I worry about this trend. This tactic not only pushes for further governmental intrusion into private lives and beliefs, it also has the potential to backfire. These chriscons trust certain "Christian" or "conservative" politicians to implement laws regulating private aspects of human behavior, never realizing that once we allow government jurisdiction over such private matters, we open the door for non-Christian, non-conservative politicians to use this new-found jurisdiction to legislate against those very Christian principles. We see this today. Christians push for laws excluding gays from marriage and certain other rights and, instead, we get laws requiring Christian businesses and churches to recognize and not discriminate against these things.
So what's the alternative? Well, the church should remain the church. There is no biblical mandate in the New Testament for the church to govern man by coercion. None. And appeals to Old Testament laws are irrelevant to New Testament Christianity. No, the church should insist strongly on the separation of church and state. The church must wake up and recognize that the only way it will be free to be the church is if it is a separate entity entirely from government. Therefore it must sever all ties with government in order to eliminate any and all governmental influence and jurisdiction over spiritual matters. The church must realize that once church and government become intertwined, government oversight of private matters is virtually guaranteed.
Instead, the church should simply do what it was instructed to do: preach the gospel, pray, give to the poor... these are the biblical principles that will change society.