American law is founded on the basis of English common law, which drew from Biblical examples to a large extent. As an example, Blackstone's Commentaries on the Law make far more allusions to Biblical verses than to secular authors. Because of the effects of the Enlightenment on American thought and the wide religious diversity of the American colonies, the Founding Fathers largely rejected the concept of union between state and church. Because of the religious diversity and the wide support for a limited Federal government, the Constitution forbade test oaths to hold public office and denied the Federal government the power to intervene in religious matters. However, the state constitutions of the Founding era mostly recognized the existence and, in some cases, the sovereignty of God and asked for His blessings. Test oaths continued on the state level until the 20th Century.
American political rhetoric from the days of George Washington to Harry Truman made frequent allusions to God, in a context usually indicating the Judeo-Christian God, and to specific Biblical passages. Even political liberals like John Kerry or Bill Clinton, despite the secular humanist bent of their political philosophy and their nonadherence to the sexual mores of their respective churches, make it a point to be seen as faithful churchgoers.
All political thought is ultimately grounded in morality, which in turn is predicated on metaphysics. The question arises: whose political thought will be reflected in the laws of the land? If secular humanists, like the RINOs in charge of the GOP, tell Christians to leave their beliefs at the church door, it is those secular humanists who are trying to foist their morality upon Christians.
Not all, but many of them. I don't see any particular moral imperative in dictating wheather I should drive on the right side of the road, or the left.
At any rate, there seems to be a degree of disingenuouness in the argument that evangelical SC's only want to advance their agenda by persuasion and not compulsion, while demanding more opportunity to try and pesuade those with the poewer to compel.