NCR chose to use the expression "hard-hearted," which -- perhaps intentionally -- hearkens back to Psalm 95 ("if today you hear his voice, harden not your hearts") and more directly to the gospels' accounts of the Parable of the Sower. In both cases, the implication is that people who disagree with God's word as interpreted by men are not listening. I think that's a simplification of reality. Most adults know that people can hear the same message and interpret it differently.