How do Trinitarians explain Jesus' response to the scribes and Pharisees at Luke 5:20-24?

Luke 5:20-24 has Jesus forgiving the sins of a paralyzed man. > "When Jesus saw their faith, He said, “Friend, your sins are > forgiven.” 21 But the scribes and Pharisees began thinking to > themselves, “Who is this man who speaks blasphemy? Who can forgive > sins but God alone?” 22 Knowing what they were thinking, Jesus > replied, “Why are you thinking these things in your hearts? 23 Which > is easier: to say, ‘Your sins are forgiven,’ or to say, ‘Get up and > walk?’ 24 But so that you may know that the Son of Man has authority > on the earth to forgive sins...” He said to the paralytic, “I tell > you, get up, pick up your mat, and go home.”" Trinitarians think that the scribes and Pharisees were incorrect here in that Jesus was not blaspheming because he was, indeed, God. Yet, instead of simply stating he was God, Jesus says something different. > "But so that you may know that the Son of Man has authority on the > earth to forgive sins ..." If the scribes and Pharisees were wrong in thinking Jesus was a man, why didn't Jesus correct them, but instead reinforce that belief by calling himself 'Son of Man' and saying he has 'authority' (why would God need to say he has authority to do something)?