Are there events too dark for a horror novel?
Yes, there are. Some real - life atrocities like extreme torture or the most heinous forms of abuse are often considered too dark. These can be so disturbing that they cross the line of what is acceptable in horror fiction, as they may be too much for the average reader to stomach and can also be seen as in poor taste.
Sure. For example, events involving the harm of children in the most brutal and senseless ways might be too dark. Horror novels usually aim to thrill and scare, but when it comes to something that is just pure, unadulterated evil without any redeeming features or deeper meaning, it can be considered too much. Horror should still have some sort of artistic or thematic value, not just shock value.
There are indeed. Take, for instance, certain historical events that are so full of human suffering and despair that to turn them into a horror novel's plot might be inappropriate. The Holocaust is one such example. While it was a horror in real life, fictionalizing it in a typical horror - novel way could be seen as disrespectful. Horror novels typically deal with the supernatural or fictionalized versions of human evil, and some events are so dark that they belong in the realm of historical study and remembrance rather than fictional horror.
