Behold the man - when PP presents Jesus to the crowd after scourging. It’s easy to interpret the statement as the introduction of the scourged man since the crowd pushed for Jesus’ punishment. I have also heard that it underscores the humanity of God (“the man”) as his suffering for our sins has begun.
What is truth - in John, Jesus has just said “…came into the world … to bear witness to the truth; and all who are on the side of truth listen to my voice”. PP’s comment seems to indicate he has doubts whether absolute truth exists. Look at his behavior as well, he acts to appease the crowd, he doesn’t really seem to show any conviction on the issue (and could probably have been swayed either way with going ahead with the crucifixion). “What is truth” is a lot like the moral relativism we suffer from as a society today; it’s a very timeless statement.