Would you say anything to parents that hosted a 16 year old's b'day party?

My daughter went to a friend's birthday party today. We had never met the parents and didn't know the girl well...so with all new friend visits to their houses...her father went to the door to meet the parents to make sure they would be there for the duration of the party. He did and felt comfortable with her staying. As best as you could feel in a 2 minute meeting...

When I picked her up she was a little weirded out because they had been allowed to watch SAW (the movie) at the girls house. And not only was it SAW...it wasn't even the rated R movie, but the NR version which is worse!

She has never seen an official "horror movie" and believe me, we are not prudes. I have let her see plenty of things....but in general PG13 is the highest rated that she sees with SOME exceptions.

I guess I'm wondering a few things...
Are you even SHOCKED? Naively I think I am...
Would you say anything to the parents?
Do you find this to be socially irresponsible to expose children to this type of film without express consent from the parents?

I am OF COURSE thankful that I have a child who tells me this sort of thing. I asked her if it was her cup of tea to which she replied, while trembling, "NO".

What the HECK is wrong with people? It's one thing to expose your own child (though I have some opinions about that as well)....but other people's children? Uh, no. GRRRRR.