What does John 18:40 mean?

The Roman governor, Pilate, has interrogated Jesus after accusations of rebellion (John 18:30–32). During that interview, it became clear that Jesus was not a political threat (John 18:33–38). The person in question, Barabbas, is identified as a murderer and rebel (Luke 23:18–19). In one sense, Pilate seems to be pushing back against the claims of Jesus' enemies. He knows, with certainty, that Jesus is innocent and that this is a personal vendetta (Matthew 27:18, Mark 15:10). By offering someone who is clearly guilty of crimes against Rome, he may be trying to outmaneuver the scribes and Pharisees.

However, Christ's enemies have assembled a mob, who will eventually threaten to riot (Matthew 27:24). They will continue to insist that Jesus should be executed for defying Roman rule (John 19:12–15). While it's clear that Pilate has little respect for the Jewish people (John 18:35), he's also in a bad political situation. History suggests his brutal, violent approach put him at risk of losing his position as governor. If civil unrest breaks out during a major religious holiday (John 18:28), and includes accusations of both blasphemy (John 19:7) and sedition (Luke 23:1–5), it will not end well for the Roman governor.

Pilate's next step will be to see if merely humiliating and abusing Jesus will be enough to satisfy the mob (John 19:1–5). It will not (John 19:6).