We know what happens: the man then rises up, and takes up his bed and walks, which proves that Jesus does have the power to forgive sins.
If He has the power to forgive sins, then, He is God.
Therefore, this is another sign that Jesus is more than a prophet, He’s more than an ordinary man, He is Emmanuel, God with us. Therefore, He is the Messiah. Therefore, He should be accepted as such, and the Pharisees should teach that He is the Messiah and uphold His position.