John comes to Jesus hoping to be commended for stopping an exorcist who was using the name of Jesus to exorcise. In his response Jesus advocates openness and allows anyone who wants to exorcise in his name to be free to do so. Since the man is using Jesus name, it is clear that he is not against Jesus and so will not speak ill of Jesus. Since he is not against, he is for Jesus.
One of the many qualities of Jesus that stood out in his life and mission was the quality of openness. He was willing to accommodate and believe even in those whom others had given up on. This is shown in his call of Levi.Matthew the tax collector and his reaching out to sinners and outcasts. In our understanding of Jesus we sometimes do him a disservice when we become too parochial and narrow-minded and imagine that he is the exclusive property of those of us who are baptised. We communicate this attitude to others when we reject their symbols of God and worse treat them as idol worshipers. We are being called through the attitude of Jesus in the text of today to make him available to all with our openness and acceptance of others and of their way of relating to God.