This could be an unending series, because there are more aphorisms uttered by G. K. Chesterton than there are days remaining on earth to mortals like myself. Nevertheless, this one is good enough to stand all by itself:
If truth is relative, to what is it relative?
That comes from a weekly column Chesterton wrote for the London Daily News, on June 2, 1906. In nine words, it encapsulates the entire fallacy of (post)modern, subjective relativism -- such as those who want to reinterpret the truth of the Bible, in order to "adjust" it "relative" to their own desires, inclinations and lives (even with the very best of intentions).
It applies equally well to those in our country's political life who claim that the Founders expressed truths relevant only to their own time, and that the Constitution is a "living" document that must be interpreted anew by each generation. And if what the Founders embodied in the Constitution and the Declaration of Independence was not any kind of "truth", but only something "relevant for their time," then forget the quaint notion that America stands for the truth. (For an example of a "relative truth" in our Constitution, good only until 1808, see how carefully Article I, Section 9 limited Congress' immediate power to address slavery.)
Whether uttered in politics or in religion -- they are the same claim, and the same same fallacy. If in doubt, reread Chesterton quote above, and try to answer his question while still making sense.