A recovery of the old sense of sin is essential to Christianity. Christ takes it for granted that men are bad. Until we really feel this assumption of His to be true, though we are part of the world He came to save, we are not part of the audience to whom His words are addressed.
If we're going to ask our kids at age 18 to go off to war and die for their country, I don't see any problem with asking them at age 16 to think about what that might mean.