Children could be open and obedient or they could be stubborn and refuse to heed their parents. Children who do not heed their parents oftentimes go astray and lead sorry lives. Jesus compared men to children who either listen and accept his teachings, or indifferent rejection of the good news he proclaims.
Just like John the Baptist, the proclamation of the good news by Jesus fell on deaf ears. This is because the Pharisees and Sadducees were insecure and threatened by the rising popularity of Jesus. They closed their hearts to his message.
If we become like the Pharisees, then we cannot hear the voice of God. How then can we joyfully share in the good news if we are proud and indifferent to Christ? Let us ask for the grace to accept Christ in our lives with open and humble hearts.