You're brain dead if you think its an "opinion" have you read the book? Did you look at the synopsis? If you did all that and still think the same then perhaps you need to rethink your life.
I understand what you are saying but its just a fantasy and it ain't real and I think that's what matters. If people want to read about rape or some type of fantasy involving rape, I think that's fine. Its definitely better then doing it in real life. If you don't enjoy these then don't read them or don't acknowledge them as it doesn't really affect people that much, at least I think - and if it does then I don't know what to say, at the end of the day its just words on a paper. As long as we understand that this is simply a fantasy/wish-fulfillment and are able to differentiate between reality and fantasy then f*ck it. Overall, people are into this because they'd like control over things they cant control in real life. This leads to why we read anything that has to do with fantasy - its because we would all love to be the man in shining armor saving the damsel in distress but a lot of us cant do that or wont so we resort to this in order to live out fantasies or get a feeling from something that ain't real even if its fu*ked up. I definitely think its a good medium considering what others do to "get off". Let me ask you question - "Would you rather people read harmless material online or act out there fantasies in real life?"