Jesus forgave sins, and passed on this power to forgive sins to the Apostles. Forgiving sin is in the purview of God, and for a man to claim that he could do so is blasphemy. Jesus needs to be God in order to do this.
SD
That is your assumption. I don't see why he would have to be God in order to represent God. Catholic priests are not God simply because they forgive sins in confession. Sins are forgiven when we repent and turn to God for forgiveness. Someone telling you "your sins are forgiven" is stating what God has already done.