The film is NOT saying fundies are right, all the contrary!!!
SPOILERS!!!
Anyone who thinks the film is a "WHAT IF" regarding BS beliefs like the rapture just didn't get the film.
It's actually a study of where such whacky beliefs can take you if taken seriously enough to their logical conclussions.
"The Rapture is vastly more intriguing if you suppose that Sharon's conversion is an elaborate self-delusion. If Sharon never has a genuine revelation but convinces herself that she does in a desperate attempt to change her life, it would explain the idiotic and unforgivable decisions she makes later, when she starts believing that God owes her something, and it would explain her attitude at the very end."
That is indeed veru true.
For how else can you explain her simply being left stranded in the desert until near death if indeed God told her to get there? Name one example in the Bible where any character directed by God to go somewhere had to wait until near death for God to show up (40 years in the dessert don't count since the israelites on that ocassion violated a DIRECT order from God, hence the 40 eyar punishment).
How else can you explain God not stopping her from killing her daughter? If God indeed asked her that, He would've pulled a Abraham ("just kidding!") and saved the girl and rewarded Sharon for her faith.
How else can you explain a TOTALLY evil God whom would ask her to kill her daughter for real and then demand her to suck it up? That's the only way to define God if everything is for real, and Sharon should be commended for telling him a big FOCK YOU. But that would be Preacher territory (the comic book by Ennis and Dillon).
Do the math, it just doesn't make any sense if indeed she was right and the rapture happened.
But if she just deluded herself (Andrea Yates, anyone?) it makes TOTAL sense. What, the "prophecies" from the boy at her community came true? True believers can rationalize anything and see prophecies fulfilled in cheese burgers. Just take a look at how many idiots think Nostradamus predicted 9/11 and even the length of my dick.
That would explain also the sherrif trying to convince her to give it up. THAT is God's true message for her, trying to get her to see the light and let up.
Some say it's a Frailty type of film (in which the dad was proven right and God indeed did ask muders and is therefore an evil God). But they miss the point in doing such comparison, because in Frailty's own logic (How can God deamnd such things?), such conclusion makes sense (main character is rewarded and indeed protected by God), but in here, the movie's own logic (can the fundies be right?) would require God to be the fundie's version, and no fundi ANYWHERE believes in an evil God, one whom would demand that much from you. Such action betrays that logic, thus invalidating the notion that indeed she was right.
But whatever. If God ever asks you other than love, seek a shrink, FAST.