Some of these reviewers have railed against feeling as though books have snuck up on them under the guise of fantasy stories and then somewhere in the middle, pulled a "bait and switch." Some have even suggested that if authors intend to have Christian content in their stories, that they should preface the book with a warning. Something like a allergen label, I guess:
Processed in a facility that may leave trace amounts of stuff that sounds and feels like the Bible.
Caution: Contains characters that bear an undeniable resemblance to Jesus or other biblical figures
Few reviewers have any problem with a religious system in fantasy. In fact, many of them applaud the depth of world-building it takes to give characters an intricate and fully-realized belief system. But if that belief system comes across in a way where the reader begins to feel the author is trying to tell him what he should believe in real life, well, look out. Those one star reviews will come hurtling in like flaming balls of catapult shot. And if that belief system reminds people of Christ, that only compounds the intensity with which people react. If there's anything reliably divisive in this world, its Christianity.
Honestly, I can't entirely blame the one-star reviewers for getting ticked off when a fantasy book suddenly starts to sound like an over-preached sermon. Themes are wonderful. Deeper meaning is what makes a good book great. But when it comes to religious content, the old mantra--know thy audience--becomes imperative.
If I'm writing for Christians, they are going to be much more willing to read an object lesson in my work and see what they can take away from that. We're used to that method of operations, since most of us engage in that exercise at least once a week if not daily. But if I think I'm writing for a crossover audience, they will drop me like cast iron that's been sitting over the fire if I start to let my characters become mouthpieces of specifically biblical teaching. This is entirely my opinion formed from observation, but I believe we all have an inner eye that recognizes our Maker, even if we are choosing to ignore him in our daily living. For those who do not have an active faith they are pursuing and an understanding of God's loving, relational nature, the detection of that God can be unsettling, to say the least.
Now then, that doesn't account for the books that are out there that, to the Body's shame, preach in the negative sense of the word, casting a reproachful, down-the-nose glance at the reader who does not align to the worldview of the story. I don't contest the single-star reward such writing earns.
The conclusion I come to is this: we need to handle all content that parallels a Christian worldview with a deft and winsome hand. It's so easy to fall into "tract mode" when we are in the territory as something as important to us as our belief systems. I sincerely believe it is far better to write a story that helps to raise excellent questions than one that tries to have all the answers.