It's meant to be shocking and serious and definitely not entertaining. It's meant to provoke discussion but what discussion? Raping kids is bad? There's not many people on the other side of that issue, and this movie isn't going to change any minds about anything.
It seems a little disingenuous when filmmakers do this, because film just isn't the right medium for these kinds of discussions. Film is the right medium for dinosaurs and explosions and spaceships. Do you honestly thing fewer kids are going to get raped because a few aficionados undertook the chore of sitting through an uncomfortable art film for an hour and a half?