I think that person is missing the concept of being fully God and fully human. It was the human aspect of Jesus which would have been tempted. It was the God aspect which would have forgiven sins. And in case this was forgotten, God is quite capable of having multiple aspects (thus the Trinity). From this, we can go to John`1:1,14. In the beginning was the Word, and the Word was with God, and the Word was God. And the Word became flesh and dwelt among us...