The young lawyer here reveals the goal of his efforts. He doesn't want or feel like he needs Jesus to justify him. He wants to justify himself, that Jesus would be amazed at his logic or his wisdom.
Jesus, though, hasn't come so that we might make good efforts at justifying ourselves. Jesus has come so that we might understand our brokenness and allow ourselves to be justified by God. To that end, he pushes, gently, on the young lawyer's idea that love has boundaries or lawyers.
Jesus tells a story about a man who is left for dead by robbers. A priest and a Levite come upon him, and they pass him by. We don't know the reasons they did -- there are likely plenty. Did they love the man like they loved themselves? It's hard for us to know the limits of our own actions. Where do we draw the lines? We always do somewhere. Jesus is trying to teach us that God doesn't draw a line. There's no limits to God's love. We can't justify ourselves -- the good news of the Gospel is that we don't have to.
