The Reverend Rankin responded again. Here is my rejoinder:
Ultimately you fail to establish your case that the God of the Bible is the only viable source for unalienable rights and that granting same-sex marriage, because it seems to contradict what the Bible says, weakens the case for unalienable rights.
First, as I've previously established on this website and which you haven't challenged, the God of the Bible never was the explicit source for unalienable rights, rather "Nature's God" was. Nature's God, by definition, is God insofar we can understand His attributes from Reason, not from faith or Revelation. "Reason" may "discover" that Nature's God and the God of Biblical Christianity are one and the same, or "Reason" may "discover" God to have attributes that absolutely contradict orthodox Christianity.
That the God of the Declaration was not defined as the God of the Bible shouldn't surprise us: Jefferson, Franklin, and Adams made up a majority of the drafting board of the Declaration, and none of them were orthodox Christians or believed the Bible to be the inerrant Word of God. And if you've read their writings in detail, you'll see that, for them, "Reason" discovered that God had attributes which absolutely conflicted with the teachings of orthodox Trinitarian Christianity (see this post where I discuss Adams explaining to Jefferson that "the laws of Nature" revealed "Nature's God" to be unitarian, not trinitarian, in His attributes).
Now, you seem to draw a distinction between "doctrine" and "history." If I understand your argument, you would assert that regardless of doctrine, the majority of the American population, when the Declaration was written and up to the present, understood "Nature's God" to be the God of the Bible. Perhaps this is so (I'm not sure if I would grant the majority of the signers of the Declaration understood this).
But given the uneasy tension between the proper understanding of the "doctrine" of "the laws of Nature and Nature's God" and the historical "understanding" (or misunderstanding) that the Declaration's God is the God of the Bible, contradictions -- for instance like same-sex marriage being understood as a "civil right" when the God of the Bible explicitly forbids homosexuality -- should be expected. Indeed, the entire theory of the God of the Bible granting unalienable natural rights is itself fraught with such potential contradictions. And some smart social conservatives understand this and hence downplay the importance of the Declaration as a "foundational" document.
For instance, Robert Locke writes:
But the Declaration says that men are endowed with these rights by God, not by the social contract. This is a puzzling assertion in light of the fact that God was worshipped for 4,000 years without anyone noticing that He had endowed man with unalienable political rights. The Bible does not mention social contracts (of Locke's variety) or democracy. When it does discuss governments, like King David's Israel or the Roman Empire, it not only does not say that they derive their just powers from the consent of the governed, but frequently intimates quite otherwise.
Thomas Fleming writes:
Whatever Mr. Jefferson and his colleagues thought they were doing (other than restating Enlightenment platitudes that have nothing to do with Christianity), they were not writing the fundamental law of a nation that did not yet exist. If they had been intending to establish Christianity at the center of the American system, they would have used Christian language instead of such deistic phrases as "Nature's god."
Robert Bork makes similar points in Slouching Towards Gomorrah where he writes: "Jefferson was a man of the Enlightenment and the Declaration of Independence is an Enlightenment document." And further, "The 'unalienable rights' of the Declaration turned out, of course, frequently to be alienable. The Fifth Amendment to the Constitution, for example, explicitly assumes that a criminal may be punished by depriving him of life or liberty, which certainly tends to interfere with his pursuit of happiness."
Nowhere in the Bible (especially the Old Testmanent!) does it state that God grants man unalienable rights, especially not the right to worship as one chooses. Indeed, the God of the Bible seems to be the very opposite of a rights granting God -- rather He is a jealous duty demanding God! The very heart of unalienable natural rights are those of conscience, which hold that God grants men the right to worship, not just the Christian God, but false gods or no god at all. Such behavior not only violates the Ten Commandments (which homosexuality doesn't), but also (like homosexuality) merits the death penalty in the Old Testament.
So from the very beginning, the notion that the true God, if He is the God of the Bible, grants men unalienable rights contained theoretical contradictions that were every bit as great as the Biblical God granting the right to homosexual marriage.