It's a psychopathic killing simulation dude, you're really stretching here. If that isn't as close to objectively repulsive as it gets then you've probably gone too deep in philosophy class for your own good.
By the same logic, you could call the viewers of Man Bites Dog & Philosophy of a Knife, and readers of American Psycho the same. The fact that the player is more active participant doesn't change anything.
Everyone doesn't have the same treshold for what's repulsive, and that doesn't make them any less sane than those who are easily disgusted.
Photographs of physical oddities (in the case of Witkin) intended to illuminate often hidden parts of society and human life in general is not in the same as a person who makes games that people play for fun saying things like "Lol our violence is tasty
"
Additionally, none of those artists would say what they were doing is purely for entertainment purposes. The Hatred developers explicitly state that on their site. It's for fun, entertainment, a 'pure gaming' experience. It's explicitly NOT designed to be challenging intellectually or artistically.
Not the same of course, but in the context of games Hatred is going beyond the boundaries just like Vienna Actionists did break the taboos of art back in the day. Although, Destructive Creations isn't doing it quite as elegantly, as they did.
As for what the Vienna Actionists said about their art...
"The profession to practise art is the priesthood for a new view of existence. The means for a profounder, intenser rapture within life and must be intensified to the point of a shameless, analytical exhibitionism, that demands the sacrifice of total self-abandonment."
- Hermann Nitsch
"Art is flesh and blood."
- Rudolf Schwarzkogler
It can have deeper philosophical meaning to the artist, or be an entirely cathartic exercise, or just a means to piss on the cultural icons and norms
