I have great difficultly explaining to people why I can watch or read some things and not others. I cannot read horror and I cannot watch horror films, even the ones that people find "funny". To me they are not funny.
However, not all violence bothers me and I can find gruesome post mortem scenes fascinating. For me it all depends on the tone of the rest of the programme. Context is everything. We do watch "Silent Witness" (though that is on the edge of what I can tolerate), but I don't watch the American CSI series, not because they're more gruesome (which they aren't really), but they're slicker and the whole thing seems exploitative somehow.
We are currently watching an excellent Danish series called "The Killing" which is about the hunt for the murderer of a teenage girl. Unlike the American shows (and some of the British ones) where one body is never enough and they have to keep the deaths coming to ramp up the tension, the writers of "The Killing" have gone the other way and are really exploring the characters and revealing interesting layers that aren't apparent at first sight. Not only that, but the detective in charge of the case is a woman who is neither glamorous, kick ass nor a harridan. She is a normal sort of woman and though she's a single mum with a family life, she doesn't angst all the time about how bad a mother she's being. She quietly gets on with the job.
Of course it is tucked away on BBC4 rather than on the main channels, but I am fascinated by the way all the usual crime drama conventions just don't seem to apply. It makes one realise just how formulaic many of the TV murder mysteries are.