כִּ֣י יְסִֽיתְךָ֡ אָחִ֣יךָ בֶן־אִ֠מֶּךָ אֽוֹ־בִנְךָ֨ אֽוֹ־בִתְּךָ֜ א֣וֹ ׀ אֵ֣שֶׁת חֵיקֶ֗ךָ א֧וֹ רֵֽעֲךָ֛ אֲשֶׁ֥ר כְּנַפְשְׁךָ֖ בַּסֵּ֣תֶר לֵאמֹ֑ר נֵֽלְכָ֗ה וְנַֽעַבְדָה֙ אֱלֹהִ֣ים אֲחֵרִ֔ים אֲשֶׁר֙ לֹ֣א יָדַ֔עְתָּ אַתָּ֖ה וַאֲבֹתֶֽיךָ׃
If thy brother, the son of thy mother, or thy son, or thy daughter, or the wife of thy bosom, or thy friend, that is as thine own soul, entice thee secretly, saying: 'Let us go and serve other gods,' which thou hast not known, thou, nor thy fathers;
Shemirat HaLashon
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.