I think that morally, there is a difference between:
a) a storyline involving immoral acts (including sexual abuse, violence, murder, etc) as part of a true reflection of life (which unfortunately involves all those things), and happens to incorporate them into a story.
b) a story particularly and pointedly focusing on something abusive or immoral in a titillating manner for the purposes of furthering a fantasy for sexual or sadistic pleasure.
I don't think there is anything wrong with a), and I think it is a good thing that even the dark aspects of humanity can have a light shone on them, lest many of us just lapse into ignorance/denial.
However, b) is where it gets controversial for me. Most times, I wouldn't advocate the condemning of any activity (however distasteful) as long as someone isn't harmed. But I'd worry about this kind of material 'stoking the fire' in people who do harbour desires to hurt/abuse others.
I'm also not sure about the road it could lead us down. Would computer-generated child pornography be ok? (god, that makes me shudder, but technically victimless). What about child sex robots? (already discussion about this happening).
I guess for me, the crux of it would be whether those things would contribute to a deterioration in human depravity, and therefore increase the likelihood of actual harm happening (I think this is likely), or whether they would function as an outlet and reduce it (I think this less likely, as generally fantasy, particularly sexual fantasy seems to escalate).