The problem that many people have with this title is that the only goal is to cause as much physical harm to other individuals as possible. There is no story, they aren't "bad guys" or zombies, and there is no core goal outside of killing people. It's a fairly disgusting game, and it's one that sets the medium back 20 years. In light of past and recent events (Columbine, 9/11, School Shootings, mass executions in the Middle East, Charlie Hebdo) this doesn't need to exist.
At best this satisfies certain individuals hunger to thrill kill, and at worse it can be used to "train" someone mentally to pull off a similar attack. I am all for violence in games, but not this shit.