The Harsh Reality of Delusion

By perchance I recently saw an episode of Dr. Phil on the goggle box.

He had a sixteen-year-old black girl on the show and, I mean she was as black as the ace of spades, you know, you could only see her when she smiles.
She was a very pretty girl, well-groomed and obviously very intelligent (she must be an atheist).

But, what the heck? She is adamant and insists that she is white!
She says that she hates blacks because they are low-class, over-populate prisons, you know; all the usual anti-black bigotry.
Her family resents her as do other decent black folk in her community proud of their heritage.

Dr. Phil put it to her that she is deluded, and her response was that she is too intelligent to be deluded. Of course, the good Doctor put her in her place stating that delusion knows no intellectual boundaries.
So, do you see where I am going with this?
I got to thinking that, here is a parallel with believing in God. As we all (should) know, there is no such thing as God as sure as this girl's skin is black yet, there are people out there who will adamantly swear that there is such a thing out there, somewhere in the ether or other dimension, or being experienced, somehow.

Whatever the case, isn't it frightening to realize how delusion can take hold of people who would otherwise be intelligent, normal human beings?
Oh sure, we can all have delusions but in these two instances, we are talking about delusion that afflicts the subject 24/7. I sincerely hope the girl eventually accepted the intervention and got some professional help but are those who are religiously deluded prepared to do the same?