Some of the scenes are just disturbing.

That is the point. Anyone who reaches 18 goes into the corn and is consumed by He Who Walks Behind the Rows. The deity also expects his worshipers to multiply. That implies that any children are conceived from and born to those under the age of 18.

Pigs are killed in real life every day as well as young girls being pregnant. Also it was two 18 year olds having sex not children.