Regarding your manner of behavior with your parents who are not in Krishna Consciousness; I may inform you that you should treat four different classes of men in four different ways. A devotee should love God and God's devotees. A devotee should make friendship with devotees. A devotee should try to enlighten innocent persons, and a devotee should reject opposite elements. As father and Mother they should be offered proper respect according to social custom, but you cannot accept their non-Godly instructions. Best thing is, to avoid misunderstanding, to remain silent without any affirmation or negation of their instructions.
Letter to Nandarani and Dayananda, 29 March, 1968