They weren't outraged because nearly all previous Christ movies were bland and boring and none of them stuck closely enough to the gospels to make you feel for once just how cleverly the greasy, sleazy Caiaphas manipulated the Romans into killing Christ. Pilate may be weak and cruel but he's also an honest man put by the priests in the no-win situation of either crucifying an innocent man or letting him go free and thus causing an insurrection that would cost Pilate his job (and also his neck when word got back to Rome).
Caiaphas and his fellow priests, on the other hand, are far worse than cruel. They're craven, manipulative liars who shamelessly tell Pilate "We have no King but Caesar," when everyone including Pilate knows they don't believe it for a second.
I think most Jews were willing to live with the Gospel portrayal of them as long as it stayed on the printed page, but when you portray the same events as dramatically as Gibson does in "The Passion of the Christ" the mendacity of the high priests just leaps off the screen. I'm sure that's what they're upset about. Gibson's portrayal of the Gospels just has too much power.
There ya go. Mel Gibson the fifth evangelist!!! What in the world did Christians do before this benighted movie? How did we get along with only the four gospels as written? How could God have waited so long to send us his ONLY ANNOINTED FILMMAKER. Yes old Mel has really shaken up the Jews like no one else before not even the evangelists themselves. But I think you are incorrect. It was the devil walking behind the Jewish crowd that shook them up.