Consider, though, how many murder mysteries have been written and loved by the reading public for the past few hundred years. Sherlock Holmes, the various pulp detective series over the years, and many, many more. Even the Bible has its share of violence, and other oddities of human nature. In these, we used our imaginations which could be just as violent for at least some readers, I am sure.
While I agree that commercial TV, at least in the US (though there are a number of rather gruesome detective shows from England shown on public television in the US too) is often overly violent, it does seem to me that people have been entertained by murder stories for a very long time. Regarding the shows we see here in the US from Great Britain overall, I think the quality of the content is much higher than the commercial stuff we see here in the US. I do remember watching some stuff on TV when I was over there, that was just as dumb as what we often have, so I assume they "cherry pick" the good stuff to show here on our public TV stations.
For those unfamiliar, public TV and radio are consumer-supported stations with much educational content and generally higher quality overall programming than one sees on commercial TV. Without delving too far into politics, I will say these stations often do have a definite liberal bias in their reporting.
https://www.pbs.org/
https://www.npr.org/
Comparing books to TV shows is a bit, in my mind, somewhat similar to what I described about the previous generation in another post in another thread - they could talk "dirty" all they wanted (and they "wanted" quite a bit), as long as they talked around it without saying the actual words. That made it OK. So here, as long as it is written in a book, it is fine, but show it on TV and it is too violent, or just too much interest in killing.
The thread raises the age-old question - is the media driving the violence or is the media reflecting the violence in our culture?
To me, it is a closed-loop feedback system where they drive each other endlessly in an upward spiral. The programming must have more and more to satisfy as we become desensitized to what has already been watched the previous season. I mentioned that books have long been written about murder, but the rise in violence in our culture to the level of today is a more recent situation. So one could argue that having murder mysteries and detective stories that featured killing, didn't cause widespread violence in our culture. TV, on the other hand, shoves it right into our faces and there is, in my opinion, a desensitizing effect toward violence that one doesn't get from reading a book.
Tony