That explains it
Now I know why I've never watched Exorcist II: The Heretic -- I somehow knew that it was a crappy movie. Tonight I just tuned in AMC as a lark and saw Richard Burton (there's a name that is supposed to mean quality) in front of the worst rear-projection scene made since the technique was invented. The following 10 minutes weren't any better. And the split screen composites used throughout were abominable. How they talked Max von Sydow (better than Burton any day) into coming back for this one I'll never know. My sympathies go to him, Louise Fletcher, Ned Beatty, James Earl Jones, Paul Henreid, and more, a veritable Who's Who of Hollywood talent. This cast was abused, pure and simple. The IMDB reports "On the night of the premiere, the movie was literally laughed off the screen. Things were tolerable until the 'synchronizer' machine was introduced, and it when straight downhill from there."
Then there's the theology. The Pope had to have excommunicated everyone involved with this one, even if they didn't belong to the Church. No, demons aren't proprietary to Christianity, but some of the things the movie shows the Church supporting are unthinkable. Director John Boorman should be given over to the Spanish Inquisition.
There's one caveat, though: Linda Blair all grown up (18 years old then) is pretty good looking.