Personally, I don't consider WWII the apex of moral society. I'm no expert, but I think it's safe to say the first 50 years of the 20th century were the most blood-drenched in all of human history.
You ought to try reading some Roman history, I recommend Robert Graves' I, Claudius if you are looking for blood-drenched (especially the Sejanus era.)
I don't read a lot of crime these days (but a lot of HF Thrillers.) Funny, because I also started off reading a lot of horror around the age of 17, before progressing to crime fiction. In my mind Val McDermid is one of the goriest crime writers.
I think there's a newbie error being perpetuated with some writers. Gore and violence are mistaken for conflict, tension and story. The best thrillers are the smart ones and well-crafted, violence and gore is optional.