If there were any evidence of a correlation between violent entertainment and actual violence, or that all "violent entertainment" was somehow being created by "powerful people" with some organized agenda, you might at least have a rational premise upon which to base this conspiracy theory.
Human societies have been violent, and their entertainment has been violent, since the dawn of language. If anything, there's far less violence in modern entertainment... there just happens to also be more of everything as well.
>Ever wonder why this stuff is considered ok, but a glimpse of a woman’s nipple is not?
Christianity.
In western civilisation most people can get through life and never even come close to having to make decisions about directly committing violence.
The answer of: just don't is in fact entirely adequate - not necessarily complete but almost always the right answer.
Whereas almost everyone "does" sex at some point. But in depicting it the exact same act takes on a huge number of implications depending on context - including violence.
Ergo it's not actually so surprising it's rated the way it is - conversely I still agree the blanket R or whatever is not really helping overall.
But also, I am not sure how much your explanation makes sense. Germany has more censorship on violence and less on sex or naked things and their experience with sex is pretty much similar.
Unfortunately, whenever I ask around for recommendations or research on this topic online, people assume that I'm anti-violence.