When I say that "horror is anti-humanist," I do not mean to insult either horror or humanism. Rather, I mean that a humanist sensibility weakens horror stories. Effective horror is either theistic or nihilistic.
By humanism, I mean that optimistic, secularist, usually materialist notion that "Man is the center of the universe," the "measure of all things," the "standard of all morality." That humans are inherently valuable. I regard Jean Jacques Rousseau, Karl Marx, and Ayn Rand as humanists.
By contrast, theism places man as subservient to higher beings (God, or gods, or some supernatural power). Man has value only to the extent that God grants him value. Even demons (or evil gods) recognize man's value -- why fight for his soul if it has no value?
Nihilism, like humanism, is also materialistic and secular, but nihilism sees man as no more valuable than any other entity in the universe. Just an accident of biology, without any meaning or purpose to his life.
Humanism elevates man to the top of the pyramid. Theism places man lower down the pyramid. Nihilism sets man on a flat plain, the equal of lions, jellyfish, cockroaches, and rocks.
In most horror films, victims are threatened by an Unnatural Threat. These films are usually theistic, in that they place the victims in the context of a supernatural universe (e.g., The Sixth Sense, The Haunting, The Exorcist, The Mothman Prophecies, The Grudge, Lost Souls).
However, even as the victim is overwhelmed by superior powers, there is a certain dignity in fighting superior creatures.
In other horror films, the victim is terrorized by squalid, sordid, grubby humans. Saw, Hostel, The Devil's Rejects, and The Texas Chainsaw Massacre have no Unnatural Threat. Rather, these Naturalistic Psycho Gorefests dehumanize the victims, placing them at the mercy of mere mortals, and reduced to the status of animals. These victims' humanity means nothing, their situation hopeless (no God or Justice will rescue them). They are just another piece of meat to be slaughtered, eaten, shat out, and forgotten.
These films create a nihilistic sensibility. The protagonists' suffering has no value or meaning.
Theistic horror films evoke a "sense of wonder" as we realize our smallness before transcendent powers. Nihilistic horror films evoke a "sense of despair" as we realize our smallness before some creepy retard with an ax.
Sometimes it's hard to say whether a horror film is theistic or nihilistic. An Unnatural Threat need not be supernatural. Aliens are unnatural to our current understanding of nature (Alien, The X-Files). So too a psycho who can't be killed -- what I term the uberpsycho (Halloween). These films flirt with theism, in that they posit higher powers.
Yet some horror/sci-if is nihilistic. H.P. Lovecraft reflected a nihilistic worldview. His characters inhabit a godless universe, at the mercy of superior beings.
In any event, I can't think of any effective humanist horror films. Even if the victim wins at film's end, her journey was through either a theistic or nihilistic milieu.
This is not to say that humanists can't enjoy horror films. Horror is about the collapse of a safe, secure normalcy; the end of reality as we know it. A humanist may very likely be terrified if he (or a character on screen) confronts a suddenly nihilistic turn of events.
For more about my thinking on Unnatural Threats, the Naturalistic Psycho Gorefest, Uberpsychos, and Horror/Sci-fi (and how it differs from science fiction), see Horror Film Aesthetics: Creating the Visual Language of Fear. This blog represents a continuing discussion of my views on horror, picking up from where the book left off.