"Dirty people" provide good soil because there is a lot of fertilizer in their life... for the free gift of God is eternal life in Christ Jesus.
"Clean people" provide the inspiration to live life as a marathon and not just a sprint... for we should not grow weary in doing good.
But note the quotes.
No one, except by rejecting Jesus, can be permanently labeled as dirty. Christ absorbed your sins and your hell into Himself to take your place.
No one, except by receiving Jesus, can be permanently labeled as clean. Integrity is only truly transformational when you are viscerally aware of your need for God.
Therefore no one will be declared righteous in his sight by observing the law; rather, through the law we become conscious of sin... or all have sinned and fall short of the glory of God, and are justified freely by his grace through the redemption that came by Christ Jesus. (Romans 3:21, 23-24)