It's your assumption because someone doesn't like a subject, that they can't be objective which is totally untrue. For example I read another infidelity fic this morning and had a completely different opinion even though it's still a subject on infidelity and I still have the same feelings on the subject. You may not believe that readers can be objective enough, but I am quite capable of separating personal opinion from objective critique. I can compartmentalize my personal feelings away from how well a story fits a prompt or genre and I vote accordingly. I'm sorry you don't believe it possible for readers to do this.