Was their complaint that Jesus called Himself Messiah? I don't remember reading that.
I remember that the Pharisees expressed their concern that they would "lose their nation and their place". So that if Jesus because a populist leader, the Romans would do like they did, put Him down by force.
But I'm asking specifically about Jesus saying He is the Son of God.
John 10:33-39 KJV
33) The Jews answered him, saying, For a good work we stone thee not; but for blasphemy; and because that thou, being a man, makest thyself God.
34) Jesus answered them, Is it not written in your law, I said, Ye are gods?
35) If he called them gods, unto whom the word of God came, and the scripture cannot be broken;
36) Say ye of him, whom the Father hath sanctified, and sent into the world, Thou blasphemest; because I said, I am the Son of God?
37) If I do not the works of my Father, believe me not.
38) But if I do, though ye believe not me, believe the works: that ye may know, and believe, that the Father is in me, and I in him.
39) Therefore they sought again to take him: but he escaped out of their hand,
Why was it blasphemy for Jesus to say He is the Son of God?
John 19:6-8 KJV
6) When the chief priests therefore and officers saw him, they cried out, saying, Crucify him, crucify him. Pilate saith unto them, Take ye him, and crucify him: for I find no fault in him.
7) The Jews answered him, We have a law, and by our law he ought to die, because he made himself the Son of God.
8) When Pilate therefore heard that saying, he was the more afraid;
Why did they demand His death because "He made Himself the Son of God"?
Why did they say,
John 10:33 KJV
33) The Jews answered him, saying, For a good work we stone thee not; but for blasphemy; and because that thou, being a man, makest thyself God.
Why was it blasphemy to declare Himself the Son of God?
Much love!