As a person who grew up with unrestricted access to violent media, I argue against this point.
I was watching violent and bloody films like Blade, Kill Bill, From Dusk Till Dawn around the time I was 5. There are a host of violent games avaliable from that time, too.
I feel like there are two reasons one would seek this type of media out: the aesthetics of violence (there’s a reason John Wick has 4 films) and genuine psychopathy, a craving to emulate.
I’d argue very few people have an actual craving to emulate extreme violence, even in an environment saturated with its artificial presentation, and that those people would do so without the access to said saturated media. I blame the parents mostly. It’s not the movies that make the attitude for how to treat others, it’s how you’re shown to treat others in real life