The arousal of defensive aggression via propaganda and social circumstances conducive to propagandistic coercion:

The arousal of defensive aggression by means of brain-washing can occur only in humans. In order to persuade people that they are threatened, one needs, above all, the medium of language; without this, most suggestion would be impossible. In addition, one needs a social structure that provides a sufficient basis for brainwashing. — Ibid

Character-conditioned passions linked to existential needs:

To put it briefly, instincts are answers to man’s physiological needs, man’s character-conditioned passions are answers to his existential needs and they are specifically human. — Ibid

Existential emptiness as the source of the destructive impulse:

Instincts are a purely natural category, while the character-rooted passions are a sociobiological, historical category. Although not directly serving physical survival they are as strong— and often even stronger— than instincts. They form the basis for man’s interest in life, his enthusiasm, his excitement; they are the stuff from which not only his dreams are made but art, religion, myth, drama— all that makes life worth living. Man cannot live as nothing but an object, as dice thrown out of a cup; he suffers severely when he is reduced to the level of a feeding or propagating machine, even if he has all the security he wants. Man seeks for drama and excitement; when he cannot get satisfaction on a higher level, he creates for himself the drama of destruction... — Ibid

"Character" defined:

While the concept of character will be discussed at length further on, it will suffice here to say that character is the relatively permanent system of all noninstinctual strivings through which man relates himself to the human and natural world. One may understand character as the human substitute for the missing animal instincts; it is man’s second nature. — Ibid

Suggestibility in connection to the existential need for "a cohesive frame of orientation":

Part of the answer lies in the suggestive influence of leaders and in the suggestibility of man. But this does not seem to be the whole story. Man would probably not be so suggestive were it not that his need for a cohesive frame of orientation is so vital. The more an ideology pretends to give answers to all questions, the more attractive it is; here may lie the reason why irrational or even plainly insane thought systems can so easily attract the minds of men. — Ibid

Distinction between the sadistic and normal character types:

In a sadistic person, for instance, the sadistic drive is a dominant part of his character structure and motivates him to behave sadistically, limited only by his concern for self-preservation. In a person with a sadistic character, a sadistic impulse is constantly active, waiting only for a proper situation and a fitting rationalization to be acted out. Such a person corresponds almost completely to Lorenz’s hydraulic model (see chapter 1) inasmuch as character-rooted sadism is a spontaneously flowing impulse, seeking for occasions to be expressed and creating such occasions where they are not readily at hand by “appetitive behavior.” The decisive difference is that the source of the sadistic passion lies in the character and not in a phylogenetically programmed neural area; hence it is not common to all men, but only to those who share the same character. — Ibid

On the existential need to "effect":

The adult, too, feels the need to reassure himself that he is by being able to effect. The ways to achieve a sense of effecting are manifold: by eliciting an expression of satisfaction in the baby being nursed, a smile from the loved person, sexual response from the lover, interest from the partner in conversation; by work— material, intellectual, artistic. But the same need can also be satisfied by having power over others, by experiencing their fear, by the murderer’s watching the anguish in the face of his victim, by conquering a country, by torturing people, by sheer destruction of what has been constructed. The need to “effect” expresses itself in interpersonal relations as well as in the relationship to animals, to inanimate nature, and to ideas. In the relationship to others the fundamental alternative is to feel either the potency to effect love or to effect fear and suffering. In the relationship to things, the alternative is between constructing and destroying. Opposite as these alternatives are, they are responses to the same existential need: to effect. — Ibid

On the existential power of boredom and the profound existential need not to be bored:

One may state that one of the main goals of man today is “escape from boredom.” Only if one appreciates the intensity of reactions caused by unrelieved boredom, can one have any idea of the power of the impulses engendered by it.

Usually overlooked in the discussion of the effect of the portrayal of violence is that inasmuch as portrayal of violence has an effect, boredom is a necessary condition.

In either instance the bored person himself produces the source of excitation if it does not offer itself ready-made. The bored person often is the organizer of a “mini-Colosseum” in which he produces his small-scale equivalents of the large-scale cruelty staged in the Colosseum.

The motive for these killings does not seem to be hate, but as in the cases mentioned before, an unbearable sense of boredom and impotence and the need to experience that there is someone who will react, someone on whom one can make a dent, some deed that will make an end of the monotony of daily experience. Killing is one way of experiencing that one is and that one can produce an effect on another being. — Ibid

Fromm's position is that malignant aggression, as exhibited by humans, is "virtually non-existent" in the animal kingdom. I accept your example of cattle-poaching wolves as a possible exception. — ZzzoneiroCosm

Does "malignant aggression" consist in taking pleasure in inflicting suffering? The question would then be as to whether predatory animals which "toy" with prey, slowly killing and then perhaps not eating the prey, or even just killing prey and then leaving it, are taking pleasure in inflicting suffering.

Why do they not consume their kill? Are they saving it for later, or is there some other reason? Perhaps they enjoy the 'sport', but do they actually conceive of the prey suffering, of 'punishing' the prey, and take sadistic pleasure in that? I doubt the last is the case.

As to the aggression displayed by social animals, I think that is plausibly understood to be a modified or elaborated form of the "fight or flight' kind of aggression, which is driven by fear or insecurity and by the need to establish social hierarchical order.