This debate isn’t likely to go away any time soon. It’s been around for hundreds of years, and will doubtless plague us hundreds of years from now.
For anyone who thinks violence in media is a new development…
Ancient
In Oedipus Rex, the title character kills his father, sleeps with his mother, and gouges out his own eyeballs after his mother commits suicide.
Heracles (or the Roman Hercules) strangles a serpent in his crib before going on to a life of murder and mayhem. And Orpheus is torn to pieces by the Thracian Maids and thrown into the river after he rebuffs their advances.
In Homer’s Odyssey, several sailors are devoured or drowned in the Scylla/Charybdis encounter. Odysseus also blinds a giant by shoving a burning log into its eye. When Odysseus finally returns home, he slaughters a roomful of would-be suitors to his ostensible widow. (And The Odyssey is less violent than The Iliad.)
See also The Epic of Gilgamesh, the plays of Seneca, and the Christian Bible.
Renaissance and immediately following
Thomas Kyd’s The Spanish Tragedy. Deaths by stabbing, hanging (two, both onstage), torture, shooting, and suicide. A character writes a note in her own blood. (See also The Revenger’s Tragedy, an even more gruesome drama. Authorship debated.)
Shakespeare, of course. Even the comedies.
Selections from Jacobean tragedy: In 'Tis Pity She’s a Whore, a brother and sister commit incest (onstage). The bloody play winds up with the brother killing the sister and coming into a party with her heart on a dagger. The White Devil: Body count = half a dozen, most onstage (poison, stabbings, etc.). Also features prostitution and corrupt church officials.
…And this is just in English.
Approaching today
The Brothers Grimm. Voltaire. Jonathan Swift. Italo Calvino. And so on. And so on.
I personally believe the causal link to be tenuous, at best. Rather, our storytelling reflects our preoccupations; you don’t blame the barometer for the hurricane, do you?
The bottom line, as I see it, is this.
We will always have violence in storytelling because violence is always the solution of last resort. Negotiations fail? Send in the army. Can’t convince someone to apologize? Punch them in the face. Want something from somebody, but have no reasonable way of getting it? Kill them and take it.
No matter how elevated the society, no matter how subtle and advanced the interpersonal negotiations and diplomacy, overt strength is always, always, the trump card, particularly (or even solely) in the short term. Why? Because we’re basically big-brained chimps, and the primate that most effectively combines brains and a lot of brawn will always dominate the group.
And drama is always, always, most effective when it tells stories in extremis. Which makes the better story, a mother worried about her child’s skinned knee, or a mother desperate to save her child’s life? Which makes the more compelling plot, a secret agent who wants to plant a bug on a world leader, or an assassin who wants to kill the leader?
I have no doubt that the debate over violent storytelling reflects a fervent wish on the part of humankind to be better than we really are. Unfortunately, until we reach that goal, we will always be seduced by blood. Everything else is just hand-waving.