I found Haneke's commentary about the viewer and violence in films, most disturbing and key. For instance, I didn't find the actual film, on the surface, that disturbing nor scary, in fact, as a viewer, I felt it was seriously lacking for its genre, and found myself wanting more - to see the violence or killings on screen - to actually make the film worthwhile and satisfying. That was what was truly disturbing.
The remote control and addressing the audience all play into this. For example, when one of the killers turns to us and asks, "you're on their side, aren't you?". Of course we'd all like to think we are - but are we? If we were, we wouldn't have chosen to watch this film about a family invasion/torture (or any other thriller/horror film), for entertainment in the first place.