I think this was originally Carrier:

When Mark says the Roman governor Pontius Pilate had a custom of releasing a prisoner on the annual holiday and the Jews cried for Barabbas, and to crucify Jesus in his place (Mark 15:6-15), what we have is surely a myth and not fact.  No Roman magistrate (least of all the infamously ruthless Pilate), would let a murderous rebel go free, and no such Roman ceremony is attested as ever having existed.  But the ceremony so obviously emulates the Jewish ritual of the scapegoat and atonement, in a story that is actually about atonement, that its status as myth is hard to deny.  Barabbas means “Son of the Father” in Aramaic, yet we know Jesus was deliberately styled the “Son of the Father” himself.  Hence we have two sons of the father, one is released into the wild mob bearing the sins of Israel (murder and insurrection), while the other is sacrificed so his blood may atone for the sins of Israel.  This is an obvious imitation of the Yom Kippur ceremony of Leviticus 16, when two goats were chosen each year, and one was released into the wild bearing the sins of Israel, while the other’s blood was shed to atone for the sins of Israel.  Conclusion?  Mark crafted a mythical narrative to convey what Hebrews 9-10 says about Jesus as the final Yom Kippur, thus telling us, with his own parable, to reject the sins of the Jews (especially violence and rebellion) and embrace instead the eternal salvation of atonement offered in Christ.  Had this story appeared in any other book, we would readily identify it as myth and not as historical fact.  As fact, it’s hopelessly implausible.  As myth it makes perfect sense.