During World War II Winston Churchill observed, "History is written by the victors." In much the same way, the viewpoint of a novel is written from the author's perspective. Evil or good is presented as the author perceives it.
What one person will find very disturbing because of past experience, another will find unremarkable. One writer may find some particular idea exciting or titillating while another can't even envision thinking about it, let alone bear to write about it.
I read a certain book about four years ago and personally, I enjoyed it. I found it very imaginative and exciting. A couple years ago, I stumbled across a review for that book that totally trashed it. Not only trashed it, but since the review was on a blog, all the blog commenters trashed it, too.
What was interesting to me, was when I dared to ask how many of the commenters had actually read the book, none of them would admit reading the book. So, what were they commenting on? The ideas in the book. In the worst form of censorship, they were rejecting the book unread based on another reader's review.
In the past few months, I found a recent review for the same book. That reviewer raved about it, praising the very same points the other reviewer hated. It was a matter of perspective.
In our character presentation we have to choose what to emphasize and what to sort of gloss over. Much of that decision is based on our personal baggage. If we've lived with an alcoholic, then our hero/heroine is not likely to hang out at a bar. If there is some form of abuse in our background, we're less likely to write about BDSM.
Every opinion is biased. When I ask my critique partners or friends or the neighbor next door to read something I've written, all of them will read it from that personal experience. It's impossible to be any other way. We are humans.