Out of respect for the person I would.
I'm still unsure about this aspect of it all. I do agree that it all must be done with respect, we all deserve that, imho, because we were all created in the image of God.
But I hesitate to use the pronouns that they inaccurately apply to themselves for several reasons. One is that is simply untrue. Remaining truthful is important to me.
Another reason is that it seems to perpetuate the, what I believe, delusion. I think that it's harmful psychologically and spiritually to affirm the delusion rather than help them see their own delusional state. I could understand how a psychiatrist/psychologist might use a modality method that includes "playing along" with a patient delusion until certain patterns emerge that can be utilized later to help dismantle the delusion... but I'm not a mental health professional.
Also, if the individual is claiming to be following Christ, I don't know any Scripture that really addresses this type of situation. I know that Jesus did interact with people that were "worldly"... "tax collectors and sinners"... but the closest thing to delusional folks that I could think of would be people that had unclean spirits; again, I have no experience with that type of thing. But there is Scripture that calls (some) Christians to confront sin in the congregation.
So, all in all, I'm left flat-footed on this issue?