Personally, I think displaying photos like the one of Black Dahlia OP described is disgusting, because it dehumanizes the victim. She was a person with a name and a life, but she's depicted as a dead, mutilated body, without the right to privacy. And for the very same reason I think allowing people to see footage of bodies in concentration camps is necessary. In case of Holocaust, it was the Nazis who stripped these people of dignity, names and, ultimately, life. Without seeing the images, it's hard to imagine the extent of what was happening in camps. There's a reason why Holocaust deniers live mostly in the US while, for example, in Poland it's practically unheard of - it's a question of availability of tangible evidence. Anyway, a while ago I saw "Night Will Fall" on TV late at night. When I started watching it I didn't quite know what I was getting into. It's basically lots and lots of footage from liberated camps, piles of naked corpses and so on, it's horrifying. And I felt horrible and disgusted watching it, but I made myself watch, because I kind of felt like I owed this to all these victims. I just checked and the movie is a little over an hour long. It felt like it was 5 hours, the emotional drain was enormous.

Anyway, I digressed, I just wanted to say that in case of Holocaust these graphic images can have an important role.