What if Jesus died for his own sins?

[Crossless2.0]

I'm holding out for an explanation of the purpose served by Jesus, the supposedly sinless one, submitting to the rite of baptism at the hand of John. Was it necessary or just a bit of exemplary spiritual theater? Somehow I doubt that the flesh-and-blood Jesus (assuming he existed) considered himself sinless, else the baptism and the so-called Lord's Prayer he taught (and, one assumes, prayed himself) really would have had no meaning in his own life.