I think this is a good topic to avoid if you can, given your audience, and your beliefs. There is literally no way you are going to be able to sand in front of any group of orthodox religious people, and get away with even implying that their religion is in any way incorrect.
In much the same way you will not be able to have a conversation with a group hardcore imperial scientists and not offend them by suggesting that a religion might be correct.
Obviously your addressing an audience and this is the exact schism that your trying to probe, but your doing so will offend.
If you insist, then stay away from words that imply fiction or myth, and address commonly accepted scientific fact, with high level, commonly accepted christian belief. You should stay away from any of the common mearicales, while avoiding any scientific theory. For example, to contrast, you could use Jonah being swallowed by a whale and the fact that it would result in death as so;
In the bible is the story of Jonah, he is swallowed by a whale. Some people have a problem with this story because they believe that Jonah was swallowed by a whale, but also believe that being swallowed by a whale, would be a lethal event. Explore cognitive dissonance here.
By exploring a single story and not addressing one group of people or another, you don't insult one group or another. In addition you allow the audience members, to exclude themselves from the group. The most fervent believer of the story will exclude him self, because he doesn't believe that this case if whale swallowing was leather. On the other end of the spectrum, the people that believe that it's not true, will continue to believe being swallowed by a whale is lethal. The people in the middle are not offended either, because you didn't call the story a lie, you just pointed out that there is some discomfort in the fact that they believe the story and believe that being swallowed by a whale is lethal.
In summary, your not going to find a word or phrase that allows you to please everyone in this context. Instead use an example or select a less divided topic.