Musar sobre Deuteronômio 13:7

And even if one sees that the din is with his father, he should see to it to quiet the quarrel and not to strengthen it against the opposing party. For aside from the mitzvah of promoting peace, he should reflect that he might be mistaken in his assumption because of the love implanted in a man's heart for his father, whom he loves as himself. As we find in Sifrei (Devarim 13:7): "'Your friend who is as your soul' — this is your father." And a man cannot perceive himself as being in the wrong.