"casual, every-day cruelty" is everyday sadism, a power play designed to bring you down and boost the abuser's feeling of mastery. The abuser may be doing it because they see someone better off than themselves and their grief and envy (their narcissistic wound) can be made better if the other is brought down. Narcissistically wounded people also try to compensate, augment their ego by joining/identifying with power centres, groups; hence an authoritarian dimension.
C. Fred Alford writes about the narcissistic wound in Narcissism : Socrates, the Frankfurt School and psychoanalytic theory (1998). He unusually defines healthy mastery and the drive for such as (positive) narcissism, while the bad effects of wounded narcissism are considered as resulting from pathological narcissism.
As Grunberger puts it, the infant is an outcast in two worlds: he is
unable to satisfy his instinctual urges in a satisfactory manner, and
he is unable to achieve narcissistic satisfaction. The result is a
humiliating sense of powerlessness, which is frequently referred to
as “the narcissistic wound,” or “the narcissistic injury.” A
quotation from Kafka serves as an epigram for Grunberger’s
discussion of this theme:
A fine wound is all I brought into the world; that was my sole
– from Kafka’s fable “A Country Doctor.”
What will ultimately compensate for this injury to some extent is a
sense of “object mastery”: the ability to control one’s environment
Power as capability and mastery of environment is the primary evolutionary nisus.