I haven't seen Cannibal Holocaust yet... can you cite scenes that might have that effect on an unsuspecting audience?
Cannibal Holocaust is an Italian film made released in 1980. After only 5 days of release, the prints were seized and the director (Ruggero Diodato) was arrested for creating a snuff film. Apparently the authorities thought the documentary style coupled with realistic human torture meant that he actually killed members of his cast. In fact, he had to bring cast members to court to prove that they were still alive. However, it is the cruelty to animals that really makes this film disturbing.
For the purpose of the film, many animals were mutilated and tortured. Turtles were disemboweled and decapitated as well as a rodent was skinned alive. It is these acts of cruelty that had the film banned in many countries under their animal protection acts.
The film is interesting in that it is the grandfather of latter indie films such as "The Blair Witch Project" and "The Last Broadcast" where the writer uses a documentary approach to tell a fictionalized story.
I'm curious if this style of filmmaking can happen now that the internet opens up so much of what is happening behind the scenes of today's films.