A Foma gives confidence

Vonnegut says that a "foma" is a harmless untruth that sooths simple souls.

Dennett uses the image of Dumbo believing that the magic crow feather makes him fly.

Believing that the Creator of the Universe is really on your side in your struggles to make it in the world gives you a lot of confidence. Confidence is a necessary ingredient to success in practically anything worthwhile. The belief gives confidence which breeds success which reinforces the belief.

I would leave them to their beliefs if only they would change their ways about sex, pleasure, and the planet.