When your child becomes a teenager you must stop preaching and start teaching.
I grew up in a generation where preachers and teachers were highly respected, but very different in delivery. The preacher was forceful, always passionate and dogmatic. The teacher was more conversational in tone, never overtly passionate, and allowed questions.
Raise your voice with your teenager and he will turn elsewhere for advice. Learn the art of asking questions. For example, “How do you think most students reacted to the burning of the American flag last week?” Affirm their ideas before sharing yours. “That’s an interesting way of looking at it. Let me share my perception.” With teenagers, conversations are more effective than sermons.