What are the main conclusions on the psychological and social causes of genocide drawn by Jacques Semelin in Purify and Destroy?

Purify and Destroy compares atrocities like the Holocaust, the Rwandan genocide, and ethnic cleansing in Bosnia-Herzegovina while respecting the uniqueness of each phenomenon. The author, Jacques Semelin, uncovers the sociopolitical processes that birth extreme violence and genocide.Semelin uses contemporary history, but also social psychology and political science, to identify the main steps in a process of annihilation. Semelin uses the term "delusional rationality" to describe the model by which fear response and resentment lead to mass killing of a particular group. Semelin further explains how ordinary people can become perpetrators of extreme violence. He develops an intellectual framework to analyze the entire spectrum of mass violence.
Semelin concludes that massacres are mainly born out of a mental process—a way of stigmatizing and debasing the "other." This, he believes, sets the stage for mass violence. The idea that those who are different should be obliterated creates collective trauma in a nation or community. The social and political actors who perpetuate these ideas take advantage of the strong emotions associated with large-scale trauma. The end result is the desire of the wounded society to destroy what has been pinpointed as the source of fear or disgust. Semelin breaks this model down into three core themes: identity, purity, and security. An outlying group is identified, a desire to cleanse society of this group is fueled, and drastic actions are taken to restore the society's comfort. These three themes are the psychological and social building blocks of massacre and genocide.
https://lapa.princeton.edu/content/jacques-semelin