The thing is, ranking affects how your books show up in the search for a general subject or tag. THAT'S a huge reason why a lot of people, especially authors (including myself!) are objecting. Things were so skewed because of this, that before Amazon started backpedaling, all of a sudden all the top searches for "homosexuality" were only returning anti-gay "how to save your children from being homosexual" Christian stuff. Books that treated homosexuality legitimately were being buried and kept out of front-page searches along with the so-called "smut". Unless you had the exact title/link for such a book, a random browser wouldn't be able to find it.

And yes, that's going to affect an author's sales, along with being really asinine when things like Playboy collections and dildos weren't being unranked, but targeted books (not just on homosexuality but even disabilities) were.