Why was a blasphemy to proclaim himself “Messiah” in the Gospel? Meguillah 4:8 gives the answer

[Giuseppe]

The irony of "Mark" is really great. Just as the disciples follow immediately Jesus when he calls them the first time (per Midrash from Elijah calling Elisha), with the same automatism, the high priest condemns Jesus to death because he proclaims himself Messiah.

“I am,” said Jesus. “And you will see the Son of Man sitting at the right hand of the Mighty One and coming on the clouds of heaven.”
63 The high priest tore his clothes. “Why do we need any more witnesses?” he asked. 64 “You have heard the blasphemy. What do you think?”
They all condemned him as worthy of death

(Mark 14:62-64)

Why?


According to a old tradition, the unction of the high priest foresaw the sign of a X on the forehead (more precisely, between the his eyes) of the anointed (by oil). The X is the first sign of Christos (Messiah) and also the symbol of the Crucifixion.

One who makes his tefillin [for the head] round, it is dangerous and has no religious value.
If he put them on his forehead or on the palm of his hand, behold this is the way of heresy.

(Meguillah 4:8)

H. Hirschberg considers this ritual done for the high priest not born by priests (and the Messiah is not born by priests). The tefillin for the Christians was the symbol of the Cross.


So, by condemning Jesus to death, virtually and automatically the high priest is proclaiming him the High-Priest and Messiah himself.

[Giuseppe]

This explains why Jesus calls Peter "Satan" for having he called him Messiah.

True Messiah is only who has to be anointed by the sign of X, i.e. only the Crucified Christ.

The Jesus before Peter is not still the Christ, since he is not still crucified.

So the irony here is even more great:

Peter recognizes Jesus as the Christ but he doesn't recognize that the Christ is Crucified.

The high priests recognize that Jesus is the Crucified but they don't recognize that the Crucified is the Christ.