A common myth is that people shouldn’t legislate their morality—especially Christians. But this is false as well. For as Michael Bauman explains, “All laws, whether prescriptive or prohibitive, legislate morality. All laws, regardless of their content or their intent, arise from a system of values, from a belief that some things are right and others wrong, that some things are good and others bad, that some things are better and worse. In the formulation and enforcement of law, the question is never whether or not morality will be legislated but which one.”
The law is undergirded by moral and value judgments. This is inescapable. Now, this does not mean that as Christians we should seek legislation outlawing sins like lust or gossip; but rather we should seek the passage of laws supporting human dignity, sanctity of life, and justice, while outlawing the atrocities of incest (consensual or not), child pornography, rape, and the sex slave trade. This is fully appropriate under a Christian worldview.
For more, see the chapter “Legislating Morality” in To Everyone An Answer.