Violence. In some ways, it's the easiest to write on, and in other ways, the hardest. Of course, violence is the least offensive, to everyone. There's no one I've met or heard of that would rather watch a laid-back, nonviolent film full of sex and language vs. Gladiator, Kingdom of Heaven, Saving Private Ryan (granted, that's not just violence).
So first of all, I have to wonder if it even matters what I say about violence, as it's much less a matter of principle than it is gag reflex, or taste. (Probably not a good idea to put "gag reflex" and "taste" in such close proximity. Makes me almost taste my gag reflex.)
On the other hand, I've asked the question in my life, why is there ever a need or a justification for a film that is rated R?
First of all, there can be no justification for a film that is rated NC-17. There are only a couple ways to get such a rating; none of them are helpful to a film. An X-rating goes more than a few steps too far, whatever it's being rated for.
But on the subject of, "Why must there be a justification for an R-rated film? Why can't they just be PG-13?" there are a few things to be said, relating in this particular case, to violence.
It puzzles me that the easiest of the three Nos to get an R-rating from is violence. I have seen a great many R-rated films where violence was the only "objectionable" content. To be honest, I didn't notice the difference between Gladiator and The Lord of the Rings.
I'm not interested in discussing the merits and demerits of a nationalised film-rating system, but since we have it, and since there are, more or less, standards for what can and cannot be in PG-13, PG, G, and R-rated films that's what we have to work with. Being candid here, violence makes me rather queasy, though it doesn't have to be the R-rated sort. Medical dramas, cutting people open, I don't care for; morally, there's no problem with an actor exposing his arm to be sliced open, nor for the makeup team to be involved in making it look real. Morally, there's not even a problem with it happening in the story or real life (in the case of medical drama, anyway).
But if you do find a problem with it, or simply find it unnecessary, is that objection justified? More broadly, and once again, can we possibly say there is a reason to allow things on screen we must censor from those under 17 (or unaccompanied by an adult)?
Yes. Yes there is a reason; and yes we can certainly say so.
It's probably obvious, if you think about it. Violence, and language, and sexual content, all of which are the three basic categories for what we call "objectionable content", belong in our stories, as they belong in our lives. No story removed from all violence, the crude talk of the common man, and the desires of the flesh is a story about a place without sin, which is a story that has little to do with us. Such stories have their place; many stories are written to include such things, without crossing certain boundary lines.
But as we grow older, not only does it take more than the minimum to get through our thick heads, because we're somewhat calloused, but equally valid is the fact that as we grow, we experience harder, cruder, lewder things, and our stories should reflect the reality of the world we live in. A moving story is only moving if it is relatable. The word relatable has become trite and cliché, in my opinion; I'm reluctant to use it. But there is no other word as appropriate.
The fact of the matter is we have violence in our films because there is violence in our world. Most of the time it's for the thrill of it, the excitement of the stunt, the mind-blowing SPFX; but there's no need to look at it the way the maker does. This isn't a call to search out stories full of blood and gore. For a great many reasons, I can't think of a single moment in the future in which I would actually want to watch Saw.
Before I go, I will say that equally valid is the fact that ours is a violence-desensitized culture, because of its exposure in film, and in life. We tune out; we don't care. This can go too far. Don't let it.