I think that it's time to firmly separate this type of material from the horror genre as it was classically practiced. "Horror" is about fear and the exploration of the unknown, a form of art intended to (as Edmund Burke noted in the genre's founding document) approach the sublime through the experience of terror: "Whatever therefore is terrible, with regard to sight, is sublime too, whether this cause of terror be endued with greatness of dimensions or not; for it is impossible to look on anything as trifling, or contemptible, that may be dangerous."
Hostel, Saw, and the bloody mess that passes for horror today is not horror. It does not approach the sublime; it rises not even to the level of terror. These types of film ask us not to experience terror but to feel pleasure, not to experience the transcendent sublime but to experience a visceral joy in the suffering of others. They are an inducement not to the contemplation of sublimity but to reveling in the vicious, savage ecstasy of causing others pain.
Burke, it is true, believed that pain was an essential element of the sublime; but this pain was in service of reaching the emotional state of experiencing pure terror and sublimity. It was our pain, not the pain of others, that produced this feeling. A good horror film invokes the sublime by inducing terror and pain in its viewers; a bad horror film asks us to enjoy the terror and pain of its characters while feeling no upset within ourselves. To take joy in the pain of others, merely for the sake of reveling in pain, is not the sublime. It is sadism. And that is not the horror genre at all.
So let us call Hostel and Saw and their ilk what they really are, not "horror" but "sadism." Let us recognize that this genre of films owns not Edmund Burke for its lord and master but his contemporary, the Marquis de Sade.