John 18:33-36: "Therefore Pilate entered again into the Praetorium, and summoned Jesus and said to Him, 'Are You the King of the Jews?' Jesus answered, 'Are you saying this from yourself, or did others tell you about Me?' Pilate answered, 'Am I a Jew? Your own nation and the chief priests delivered You to me; what did You do?' Jesus answered, 'My kingdom is not of this world. If My kingdom were of this world, then My servants would be fighting so that I would not be delivered over to the Jews; but as it is, My kingdom is not from here.'"
Would you have fought against the Jews to defend Jesus? Imagine you had been there that day. You see the Jews humiliating and torturing Jesus. What would you do? Would you have fought against the Jews?
Also, Jesus was a Jew, and did infer that he was an otherworldly king. That last bit was heretical, against the Roman Emperor, and their whole religious mythos. Pilot was stuck in a bad place, but had to deal with it before it grew into a larger problem. He couldn't save Jesus, though he seemed to want to find such a way. Defending this madman would just have gotten you killed, too.