Children learn from their parents and many parents today have very poor manners. We don't know for sure, but my impression after having studied the American scene for a long time, is no. Yes, I agree that there's been a coarsening of our culture and a rise of ill-mannerdness, and we all have to be concerned about that. Families don't spend enough time at the dinner table talking about such matters. In fact, it's been argued that the American family dinner hour is disappearing.
Many families have TV on during dinner.
They're not going to pick it up from the media by and large. Our schools, in my view, don't give enough attention to civility. Civility is the end product of thousands of years of humanity, and we're not giving it enough due in the schools. I don't believe that American culture is melting down. Yes, we have coarsened perceptibly, but it's not the end game.