Short answers, pulled from the story.
Robert Sternberg identified three elements in hatred: a negation of intimacy by creating distance when closeness has become threatening, an infusion of passion such as fear or anger, and a decision to devalue a previously valued object. He also described a "mutinous" variant in which a person repudiates a dependent relationship in pursuit of autonomy.
Sigmund Freud defined hate as an ego state that wishes to destroy the source of its unhappiness, linking it directly to the question of self-preservation.
Functional MRI studies found that viewing pictures of hated individuals produced increased brain activity in the middle frontal gyrus, right putamen, bilaterally in the premotor cortex, the frontal pole, and bilaterally in the medial insular cortex.
J'ai la haine translates literally as "I have hate" and describes a relationless hatred with no precise English equivalent. While English hatred always involves a relationship with a force, object, or person, this French expression names a form of frustration and animosity that churns inward without attaching to any external target.
Gordon Allport's scale measures prejudice in a society across escalating stages. Antilocution, the formal term for hate speech, is the first point on that scale, meaning it represents the earliest indicator in a spectrum of prejudice that can escalate further.
Aristotle viewed hatred as distinct from anger and rage, describing it as a desire to annihilate an object entirely and noting that it is incurable by time, unlike the shorter-lived emotional states of anger or rage.