John 19:13-16
When Pilate therefore heard that saying, he brought Jesus forth, and sat down in the judgment seat in a place that is called the Pavement, but in the Hebrew, Gabbatha. [14] And it was the preparation of the passover, and about the sixth hour: and he saith unto the Jews, Behold your King! [15] But they cried out, Away with him, away with him, crucify him. Pilate saith unto them, Shall I crucify your King? The chief priests answered, We have no king but Caesar. [16] Then delivered he him therefore unto them to be crucified. And they took Jesus, and led him away.
I have often wondered if in "acknowledging" Christ's claim (John 18:35-38) it was not more of a mocking of his own people (the Jews), than it was any sign of true faith in Jesus as Messiah.
Pilate had tried Jesus (John 18:28-19:3) and declared: "Behold, I bring him forth to you, that ye may know that I find no fault in him." (John 19:4). Yet the people said "Crucify him!"
I believe that Pilate was happy to turn Jesus over to be crucified, because if He was indeed the King, Pilate would be out of a job. By giving into
the people's demands that Christ be crucified, Pilate could "wash his hands" of the whole affair (Matthew 27:24-26) and justify himself that he "tried" to set Jesus free, but these people wouldn't allow it (just in case Caesar had something to say about it after the fact).
So, I guess I see this move by Pilate (ie--putting up this sign) as not so much an acknowledgement in faith, but rather an attempt to cover his own backside.