Parable about John the Baptist
Whenever you read "He who has ears to hear, let him hear" a parable usually follows. Jesus spoke of John the Baptist with the following parable.
Children in the Marketplace
"He who has ears, let him hear."
To what can I compare this generation? They are like children sitting in the marketplaces and calling out to others: "We played the flute for you, and you did not dance; we sang a dirge, and you did not mourn."
For John came neither eating nor drinking, and they say, "He has a demon." The Son of Man came eating and drinking, and they say, "Here is a glutton and a drunkard, a friend of tax collectors and sinners." But wisdom is proved right by her actions.
Jesus rebukes unrepentant cities
Then Jesus began to denounce the cities in which most of his miracles had been performed, because they did not repent.
"Woe to you, Korazin! Woe to you, Bethsaida! If the miracles that were performed in you had been performed in Tyre and Sidon, they would have repented long ago in sackcloth and ashes. But I tell you, it will be more bearable for Tyre and Sidon on the day of judgment than for you.
And you, Capernaum, will you be lifted up to the skies? No, you will go down to the depths. If the miracles that were performed in you had been performed in Sodom, it would have remained to this day. But I tell you that it will be more bearable for Sodom on the day of judgment than for you."
Insight 1: Hardened children
Both John and Jesus were rejected by those whose hearts were hardened.
Jesus showed how foolish these people were by comparing them to children who don't get what they expect. They rejected John for fasting and refraining from wine, and rejected Jesus for eating and drinking.
Their expectations could only result in the categorical rejection of any prophet.
Insight 2: Harsher judgement
Bethsaida, Chorazin, and Capernaum were cities in Galilee. Even though Jesus spent many months teaching and performing miracles in Galilee, he was still rejected by these cities.
Consequently, Jesus said it would be worse for them in judgement than for Sodom and Gomorrah, whom God destroyed with fire and brimstone.
This begs the question, "How will eternal punishment be worse for some than for others?" We are not told. But the Hebrew writer also indicated that punishment will be worse for those who reject Christ, than for those who are ignorant of him.
The principle is further amplified in Luke's gospel. Jesus indicated that a rebellious servant, who knows the will of his master, will deserve more stripes than one who is ignorant of his master's desires.