This happens when their negative aspect as split into two parts, in their mind one aspect is good and the other aspect is Evil.
This is how Good versus Evil is propagated, this mental disorder is called Schizophrenia and all hu-man beings suffer from this Mental Disorder.
To heal their mind they need to become Self Aware and bring their whole personality together. They do this by understanding their Personality consists of three aspects Negative/Hate, Neutral/Truth, and Positive/Love, only then they will experience Peace.