[Bruce Campbells Chin]

Someone's delusion about their gender is not my issue to sort out. Someone want to be called She despite an objective reality in conflict with it? Sure, I'll call them that, then I'll walk away and that's the end of that.

I personally still view it as a mental illness, and would be no more inclined to mock them/agitate them to their face as I would anyone else who was mentally ill.

That being said, I'd limit that to personal, face to face social encounters. Outside of that, and of course if the person in question tries to make it an issue and draw you into a discussion, I hold to biology as being determinative of pronouns.

[Malsua]

I personally still view it as a mental illness, and would be no more inclined to mock them/agitate them to their face as I would anyone else who was mentally ill.

Exactly. To do otherwise is to invite unnecessary drama or worse into your life. Get through it and move on. As a rule, I avoid mentally ill people as nothing good can ever come from it.