Institutional Christianity has had clear secular benefits to American life for hundreds of years. It's played both a prophetic role in terms of generating moral critiques of American excesses, and so on, and also a communal role, in terms of building community as the country moved westward to the role my own Catholic Church played in assimilating generations of immigrants.
You'll see a lot more blood in 'Saw' movies or something like that than you will in either of the 'Last House' movies. I kind of think it owes more to 'The Virgin Spring' which is the original source material, the Bergman movie.