To be fair, William Friedkin's response to Exorcist II is about on par with most people who have seen it. It's regarded by many to be one of the worst films ever made. Friedkin tells The Movies that Made Me podcast that the movie tries to "reverse" the work of William Blatty, the author of the original Exorcist novel which the first film was based on. Friedkin clearly has a lot of respect for Blatty, and thus has little respect for a movie that he feels has no respect for the source material.