You are right. It does feed upon itself. The same methodology of what is called deconstructionism undermines not only the Scriptures but what Christians have believed, taught, and confessed for two thousand years. That is the problem with cultural relativism. Everything become relative including morals and commonsense.
Some theological systems teach a weighing or amalgamation of Scripture, Tradition, Experience, and Reason.
In the ELCA it is clear that Experience and Reason trump Scripture and Tradition. The weight and authority accorded to each is probably—greatest to least—in the order listed in this paragraph.