"One should not dispute with those who deny first principles." I found this Latin tag in Luther's Tischreden (Table Talks) in a section entitled Unnütze Fragen (Useless Questions), Weimarer Ausgabe, III, 2844. He applied it to those who deny the authority of the Bible. I agree with the maxim but I find that the good doctor has misapplied it. One who is serious about the truth should want to enter into dialogue with intelligent, sincere, civil, and serious people regardless of their point of view, and this includes those who deny the authority of the Bible. How can one care about the truth and not want to study every philosophy, every religion, and every political ideology? Study everything! How can a serious inquirer not want to know whether what he holds to be true really is true?
But a maxim that can be misapplied can also be correctly applied. There are some principles so fundamental that they cannot be rationally disputed. Among these are the principles that make possible rational discourse. There was a nincompoop of a leftist commenter at the now defunct Right Reason once who opined that truth is a social construction. Anyone who maintains a thesis of such stark absurdity is not one on whom one should waste any words. That truth is absolute, and as such the opposite of a social construction, is a first principle to which Luther's maxim applies. If you have truth, you have something absolute — which is not to say that you have truth!