Before telling the story of Jesus being taken to Pilate, Mark takes care of the last loyal disciple. Peter was following from a distance. Three times he is asked if he was with Jesus. With increasing intensity he denies it, finally "[h]e began to call down curses on himself, and he swore to them, 'I don't know this many you're talking about.'" Just then the cock crowed, and Peter broke down and wept.
In Mark 15:1-20 we learn that the Sanhedrin takes Jesus to the Roman governor. This section is all about blaming the church establishment and excusing Rome for the execution of Jesus. No small task given that Jesus was crucified by Rome and not stoned by the Temple authorities. Nonetheless, Mark provides the following evidence for this: (1) Pilate is amazed that Jesus doesn't respond to the Temple authorities' charges; (2) Pilate offers to release a captive but that releast Barabbas, the insurrectionists who had committed murder in the uprising, instead; and (3) Even after releasing Barabbas, Pilate doesn't want to kill Jesus but the crowd chants "crucify him!"
Details first. This was written shortly after Rome had destroyed Jerusalem, or during a violent uprising. This scripture makes it clear that Christians are different from Jews and that Rome shouldn't worry about Christians. The idea that a Roman governor would be swayed by the masses asking to crucify someone is not credible. And, note that Barabbas is Bar-abba, or son of abba, or son of the father, or . . . Son of God. The Israelites reject the way of Jesus, the true Messiah, in favor of this false Messiah of violent overthrow. When compared with the apacolyptic scriptures from earlier it makes sense.
Okay, but now what does the story mean? In Catholic mass the attendees shout, "Crucify him! Crucify him!" during this part of the passion. The story calls on the reader to remember how the people abandon Christ. It wasn't really the fault of the government for Jesus' execution, it was our fault for turning our back on him.
The world is full of evil, and at times we give up. We turn our backs on Jesus' ministry. The passage calls us to remember our apathy and the wickedness it causes. It ends with more mocking, with more humiliation for our Lord and Savior.