I think the term "Separation of Church and State" has been twisted and corrupted from the time Thomas Jefferson wrote to the Danbury Baptists about it in 1802. The term is not used in the Constitution, but Jefferson used it ("building a wall of separation between Church & State") to help explain the combined effect of the Establishment Clause and Free Exercise Clause of the First Amendment ("Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof . . .").
This concept was test in 1878 before the U.S. Supreme Court (Reynolds v. United States, 98 U.S. 145). George Reynolds belonged to The Church of Jesus Christ of Latter-day Saints, and was convicted of bigamy. One of his arguments was that, as a Mormon, it was his "religious duty" to practice polygamy. Since the Constitution does not define religion, they used Jefferson's letter in it's argument against the "religious duty" claim, and ruled that "Laws are made for the government of actions, and while they cannot interfere with mere religious belief and opinions, they may with practices." In other words, if they allowed polygamy because of religious beliefs, then religion would become the supreme law of the land.
Am I for it or against it? I'm for it in the Jefferson context. I believe that the government should not sponsor any religion, nor prohibit any authentic religion (meaning you cannot start a religion for the purpose of bypassing a law). Many of our laws are based on Christian principles, and I have no problem with this, as long as it is still being respectful of other people's religions. Some of these laws I disagree with, but not because they are based on Christian principles. I disagree with them because I feel they violate some human rights (gay marriage is a good example).
Jefferson's Letter to the Danbury Baptists:
To messers. Nehemiah Dodge, Ephraim Robbins, & Stephen S. Nelson, a committee of the Danbury Baptist association in the state of Connecticut.
The affectionate sentiments of esteem and approbation which you are so good as to express towards me, on behalf of the Danbury Baptist association, give me the highest satisfaction. my duties dictate a faithful and zealous pursuit of the interests of my constituents, & in proportion as they are persuaded of my fidelity to those duties, the discharge of them becomes more and more pleasing.
Believing with you that religion is a matter which lies solely between Man & his God, that he owes account to none other for his faith or his worship, that the legitimate powers of government reach actions only, & not opinions, I contemplate with sovereign reverence that act of the whole American people which declared that their legislature should "make no law respecting an establishment of religion, or prohibiting the free exercise thereof," thus building a wall of separation between Church & State. Adhering to this expression of the supreme will of the nation in behalf of the rights of conscience, I shall see with sincere satisfaction the progress of those sentiments which tend to restore to man all his natural rights, convinced he has no natural right in opposition to his social duties.
I reciprocate your kind prayers for the protection & blessing of the common father and creator of man, and tender you for yourselves & your religious association, assurances of my high respect & esteem.
Jan. 1. 1802.