Should I always have to speak authentically? Or can I say to a lover, “What does God tell you now?—Now that you have fallen out of love with me? Am I still “the one you will marry” as he told you before? Or does he tell you now that was only a test? Or…?”
Well, I can of course ask about the speech given by God to another at any time without believing in Him myself. However, I run a risk. If I talk inauthentically then I might be quick to interpret them as offended. And perhaps I might have to react to attacks claiming that I am patronizing them. But do I have to consider myself patronizing? After all, in speaking of God inauthentically, I do make an attempt to disclose their world. And still, I can learn something by asking the question!—and not merely of their psychology, but of the world (colloquially, ‘my’ world).
The same holds for any science. I can use that language without conviction to that world, but still with a position to understand ‘my’ world.
Ultimately, this should does not come down to any ability which I may or may not have, or to any moral right to speak inauthentically.