Why does God call Ezekiel Son of Man and why does Jesus call himself Son of Man? It is a title which was not fully developed in the Old Testament but was well developed by Enoch between the testaments.
God used the term 90 times of Ezekiel to emphasize his humanity. While Jesus used it of himself in part for that reason, the idea is much more important than that. Yes, Jesus accepted his humanity, but he was also God.
Consider Matthew 12:8: For the Son of Man is Lord of the Sabbath. NIV He is not saying that we humans have control of the Sabbath, that we can do what we want. He is saying that the Sabbath was given to us by God to refresh and renew us. But it is not so restricted that we cannot do the other things God commanded, i.e., care for those in need.
Daniel used the Son of Man title in the sense of the promised Messiah in 7:13. Both Daniel and Ezekiel spoke the Word of God during the last days of the Sothern Kingdom (Judah) and the Assyrian exile of the Northern Kingdom (Israel). In the final decades of both exiles, the people of God came to understand that God would indeed renew the greatness of His people; that he would do it by sending a representative called the Messiah.
When Jesus began his ministry, the people of God had a well-developed notion of the Messiah, the Son of Man; the two titles were interchangeable. For Jesus, Enoch’s understanding fell short of completeness. Enoch stressed judgment, Jesus stressed justice.
The passage for today from Mark clarifies the difference. He was amazed at their lack of faith. NIV Jesus did not deny that judgment would occur for those who opposed God, but he preached that our failings, our sins, would be forgiven if we placed our faith in God. By stressing mercy over destructive judgment, Jesus redefined the role of the Son of Man.
Our role is to imitate Jesus, the perfect Son of Man. We are to be as much like the perfect humans that God created as possible. In that role, we are to be true friends to everyone. We must seek to do nothing that causes harm to anyone. We will often fail , but with our faith always in the Son of Man, we will join Him in that perfect New Jerusalem.
Be righteous and do good.