I marvel that the second thief was aware of his own culpability, showing that his human conscience had not yet been seared. Not only did He know of his guilt, he readily confesses it.
It seems with most people, the more they are convinced they are wrong, the more vehemently they argue they are right.
Also I wonder about the second thief's testimony in regards to the character of Jesus. Was he privy to the events of this itinerant teacher? Had he heard of the miracles? Or perhaps he had been present to observe a healing or feeding first hand. He could have been in the crowd that heard a sermon, or observed a confrontation between Jesus and the Pharisees.
I have observed frequently how the presence of the Holy Spirit in a Believer is recognized by unbelievers. Obedience to the Supernatural is provoking to the natural man. And since the power and persona of God can be convicting to others through our lives, how much much much more would the Son of the Highest exude the Eminence.
And if this malefactor could discern the uniqueness that belongs to Jesus, how condemning is this to the others?
Those who did observe the miracles of those fed and those healed—surely some of them were in this mocking and spitting crowd.