It seems to me as if the main thing the authors of this article (it's German, sorry) couldn't accept, even though they didn't say it, is not the brutal murders in the novels they write about, it's the fact that the writers are female. Women don't imagine such brutality if they're normal - this seems to be what they really think.
I happen to like Tess Gerritsen's novels. They are sometimes brutal in the descriptions of murders and suchlike, but most of all they are well written and picture strong characters - not few of them women.
And, let's face it, we are living in a brutal world. Sex and death seem to be destined to rule our lives. And if I pick up a thriller, I expect it to show me the dark sides of our real world. I don't expect it to be all fluffy bunnies and pink tutus. And for me, to show the full extend of the madness embedded in the minds of the murderers also means to show the full extend of the blood and the gore they revel in. It's not something that gets me off, but it's something I find necessary and almost normal for a novel of that kind. And I've read it in novels written by men as well.
So this seems to be what it all boils down to: those are women writing such dreadful stories (instead of the shallow love-stories and melodramas they should be writing). Not strong men who might have been cops once in their life, but women who are not supposed to be so cold-blooded and used to violence.
And from my experiences - and given the fact that, for example, most pathologists these days (which means those recording the dreadful details of a murder) are women - that's a very old point of view. Women are usually committing less violent crimes, but they do experience violence just like everybody else - if not more of it. Women are beaten more often in their family (while most men are beaten somewhere else, like a pub). Women are more likely to be raped or assaulted (sexually or otherwise). In other words: women are more likely to become the victim of violence than men, on the whole.
Still, talking and writing about violence is still seen as the domain of men (just like talking and writing about sex, but that's another topic). So it's scaring for some people to see women writing about it that easily and that successfully.
It's the 21st century, not the year 21 A.D., so learn to live with it!