The way I see it the whole enjoyment of fictional violence - no matter if it's dark humor jokes, videogames or eroguro - comes from the fact that it's fictional. Thus having violence be real would defeat the whole point. By engaging in fictional violence we're taking this thing that's meant to hurt and DEFY it by turning in it into something that not only doesn't hurt anyone but can even bring fun instead. It's a defensive mechanism of our psyche against the very concept of violence.