So their faith is right even if the church is wrong
Eddie says to Sarah something along the lines of "I believe in you, and I believe in what we do. But everything else is fairy tales." But they're not fairy tales. Eddie has a vision of Steven sick in bed, and there is no logical explanation for him to know about his leader cancer; Cal knows Eddie will have a vision when he digs that hole; Sarah dreams about the Pachamama/Medusa before she sees the figurine in her desk; and Abe's daughter heals after Eddie prays for her.
So it isn't their faith that's wrong. Cal, on the other hand is very wrong, he's a psychopath. Sarah and her parents may fill their mouths talking about love and family, but are willing to cut ties with their kids way too easily. And Nicole and Joy are two insufferable holier-than-thou bitches.