I totally disagree about the difficulty of describing horror, since the linked article is one of many to have received critical acclaim for providing quality descriptions of WW2 experiences (my recommendation is 1952's The Naked Island).
Agree about the necessity of the never again stuff though, even though we've been failing at that continuously.
Well, op may be making the point that even the best description of horror is little compared to experiencing it. Watching a video of the horror itself (e.g. combat footage, a beheading, open-heart surgery) pales in comparison to experiencing it firsthand.
Agree about the necessity of the never again stuff though, even though we've been failing at that continuously.