Well, I know you and I would not agree on a lot of interpretation of the Bible.
I am making a distinction between what laws are enforceable by man, and what laws are enforceable by G*d.
But I am asking about morality, not laws. I'm also asking about what is, not about what is enforceable.
If your argument is that religious morality should drive the enactment of laws, I then want to know what religion's beliefs would the government adopt to do so. And how they would get around the First Amendment to do it.
I am arguing that morality is nothing more than a worldview and that everyone has one. The Christian, Jew, Muslim, Buddhist, Taoist, and Atheist all have worldviews - basic assumptions about reality that drive thier notions of things like justice, rights, human worth, etc., etc. Everyone uses their moral notions when voting, lobbying, or becoming activitst.
You have no more right to tell me not to include my notions because they are Christian than I would have telling someone else not to include their notions because they are Muslim. We bring them all to the public square, debate, and the result is our law.
However, for this law to be good, the morality has to have a basis in reality. If you look at all the major religions of the world, you will find an uncanny commonality, such that Jews, Muslims, and Christians in America are often on the same side of most cultural issues.
One of these is that homosexuality is the sign of a disturbed mind, and an individual who needs help. I think we can declare sodomy illegal, make the typical response of catching someone in the act a fine and a requirement for treatment, without violating our Constitution or the separation of Church and State (and without asking people personal questions).
By the way, the "Render unto Caesar" passage to which you refer was Christ's way of reminding the Jews that they - their entire selves and lives and money and everything else - belonged to G-d. He was chastizing them for living in such a worldly fashion and pretending to be G-dly.
Shalom.