I disagree entirely.
We've been systematically exposed to murder, rape, fraud, theft, and every other crime imaginable since the day we were born. Tom and Jerry, Wile E Coyote, etc. used to "kill" each other with mallets, dynamite, whatever was to hand. Games have gone from pixels touching to realistic 3D representations of killing prostitutes while the in-game characters whine about how they got in their way, "bitch".
And yet STILL, roughly the same percentage of people ever commit those kinds of crimes. Still, in some countries, crime figures are going DOWN per person, not up.
My grandfather's generation witnessed wholesale murder and genocide the same as I do - they were sent to deal with it, unprepared and unaware, and many of them never returned from battle the same. The same could be said of their grandfathers. And the same could be said of the war in Iraq, the war on terror, Vietnam, whatever war you want to pick.
Death is a horrible, but inevitable, part of life. Witnessing death may allow you to cope with further death more easily, but it does not turn you into a murderer on its own. I'd hate to know that a kid who lead a sheltered life and never experienced violence throughout it is suddenly thrown into even a street mugging without knowledge of how that might go. It can destroy people - I've seen it happen.
Yet those who suffer the most gory of horror films, witness the worst of the Internet, actively plough through it and seek out something that others might find abhorrent? They are not automatically immune to the effects of such things happening in real life yet can cope with it much easier if it happens.
Children who have NEVER been exposed to swearing form their own. Swearing is as natural an outburst of suppressed frustration as crying. People who do not swear are, in my head, either a) lying or b) scare the absolute fucking shit out of me.
People who aren't exposed to rudeness cannot understand that it's possible, or how to deal with it, or why they should play the game that others - now demonstrably in front of them - have never.
People exposed to violence are no different. I grew up not in a ghetto with bullets whizzing past my head, but in a rough area of London. I grew up with fights in the playground, and outside it, as a natural part of childhood (for that area). I, however, am a well-adjusted adult. I work for schools (and, therefore, have not committed these kinds of things as an adult). I can sit through the goriest of movies (whether it's actually just gore, however, and boring as fuck, or the gore is just part of the otherwise-good movie is a bigger question to my entertainment of it). And I've seen violence.
The thing it does is allows you to deal with it. It does not numb you to it. And, to be honest, I'm probably one of those people who could quite easily be numb to it - I'm probably high up on the autism scale and, as my friends and family would agree, it's so obvious I don't need to go and be diagnosed as such. But, still, real-life violence is abhorrent and scary to me, even if "fake" violence in movies and games is - actually - quite humorous and blasÃ© to myself.
Yet, when there's blood, and violence in real-life, it's me that ends up phoning for help, stepping in, acting with a clear head. Everyone else is too shocked to do anything about it in time and just wants to get away from it. A good survival tactic, maybe, but not the way to handle it.
As stated for everything from your parent's smoking (my mother smoked incessantly basically from her pregnancy with me to today), parent's drinking (my father worked in a brewery and used to be paid in beer tokens so we were never without alcohol), your friend's jumping off bridges, your video games depicting violence, your movies trivialising abhorrent crimes, etc. JUST BECAUSE YOU SEE IT DOES NOT MEAN YOU WILL DO IT.
You have to be seriously maladjusted for something you witness to cause you to perform that same, or similar, acts as an adult. Children, possibly, but that's why we insulate children from these things and clarify the boundaries of real life versus what's acceptable in video games. However, seeing it can make you deal with it much better - in the same way that going on a first aid course will NEVER prepare you for your first blood-soaked granny lying on the ground. But see enough of them, and it becomes "just another patient".
Humans can be fucks. They can also possess empathy like no other species is capable of. No other species will organise and rally round after a single member of theirs is captured by an "enemy" in order to return them to freedom, no matter how many years it takes. No other species.
Humans, by their greatest power and possession, have the ability to reason through situations and distinguish reality from falsehood. Swearing in front of child does not make it a swearer - you know what does? Acting like it's the worst thing in the world that they've picked up a word they don't know the meaning of. THAT's what gives them the knowledge that it has power, and will encourage them to use it.
For millions of years, humans have done all these things. Never before have we ever had so many humans, so close together and so little crime (proportionally). Because we are now able to simulate situations to such an extent that we don't have to imagine the consequences, we can see them for ourselves. And that same horror translates into our brain as it would after the first PHYSICAL viewing of such events, which gives us a headstart.
Seriously, blaming the media is an easy target. The real culprit is "humans" however, and you're one of them. There are parts of that to be ashamed of, sure. Inevitably. But people watch these things because their minds want to watch them. And people have gloried in the macabre and obscene since they first learned to walk. But it does not make them murderers, attackers, rapists, violent or insensible. It just helps them deal with those who are.