People react to Jesus in different ways in Matthew's Gospel. We read of them being jealous. People are often amazed or surprised by things Jesus says and does. In this passage, Matthew shows us that people are afraid of Jesus. This is important to remember for those who would follow Jesus. He is the savior. He offers that we can be his friends. Still, he is also always our master and the one coming to judge us in the end.
Though disciples are not to be judgmental of others (Matt 7:1-5), Jesus does teach us to know who we are dealing with. The Kingdom of God is precious, and its resources are not to be treated casually or carelessly. Some situations might only be a waste of time, or, worse, putting Kingdom things at risk of being abused and mistreated. Disciples are to have some "street smarts" as we go about our mission for the Lord.
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.