Recognising the truth through refutation:

Neither those very replies nor those critiques, taken on their own, harm anyone on either side—be it the critic or the one criticised. For truth is discerned by its own light and proofs, not by whoever parrots or proclaims it, at least in the view of the fair-minded, though not in the eyes of the prejudiced and arbitrary. What truly harms people is speaking without knowledge, hurling words at random, and addressing the servants of Allah without right.