Mercy is at the heart of everything Jesus did. This was on display when Jesus called Matthew, the tax collector, to be a disciple. Many other sinners came to Jesus, too, and found his mercy.
Disciples of Jesus are as prone as anyone to make judgments about others. In this passage Jesus teaches us to pay attention to our judgmentalism. It might be a sign that we have much bigger issues in ourselves than those we call attention to in others.