You're right, it's an absolute double-standard. That should be the basis for the uproar.
I have a hard time with people who are upset about the movie because some people, even Christians, will believe that this fictional account of Jesus is real. There are already many current myths about Jesus, and anyone who gets their information about Him from a movie is a ding-a-ling.
We can't wipe out ignorance, but we can stand up to the promotion of double-standards.
I agree that the double standard is the issue here. Had a similar film been made about Islam, it would never see the light of day. As with the Danish cartoons, it would be supressed at the altar of "religious sensitivity". A sensitivity that appears to only be applicable to muslims.