In his response Jesus uses the image of a doctor (physician). A doctor is not called to healthy people, but to sick people. This is exactly how Jesus came for sinful people. But then you must be willing to admit that you are a sinner, just like a sick person must admit that he is sick! The leaders of the people lacked this. They considered themselves healthy, that is, righteous before God.
17 And when Jesus heard it, he said to them, “Those who are well have no need of a physician, but those who are sick. I came not to call the righteous, but sinners.”