AS I mentioned earlier, I'm Jewish, so my view differs from that of most of those who have commented on this subject. I am willing to consider other sources and evidence, for instance.
But for the true believer, the Bible literalist who, like Mr. Gibson, considers the Gospels to be the inerrant, inspired word of G-d, the concept of historical accuracy is confined to maintaining consistency with the four Gospels to the greatest possible degree. Judging it by any other standard is equivalent to criticising a production of, for instance, "Hamlet" for its violence. The fact that he read and studied other sources to learn how others had interpreted the same source material does not detract from the seriousness of his attempt at scriptural fidelity.
What he has done is to take a relatively sparse description of events and add the detail that he envisioned to create the visual scenes, the dialog, and some of the in-between events that are not described but provide continuity for what is there. Literary license? Of course. But did he insert material that is inconsistent with the source material, or omit anything critical to a reasonably complete exposition of the Gospel story?