The mind can rationalize anything away, even beheading children. You were just cleansing the world of evil. Beheading children is a good thing. A just thing, and you are a righteous man for doing it.
I think that is explaining the fact of something by a description of it. It does not tell him why one person can believe in beheading and why another does not. We need to understand that actions have motivations and how those motivations come into being. It seems to me that I did explain that to him.
Human beings are animals composed of a reptilian, a mammalian, and a human brain and that brain is bicameral in nature. Each hemisphere is capable of containing a separate independent consciousness, one that is dominant vis-à-vis its counterpart in language, the self we know ourselves to be, and one that is basically silent, that one much better at linear thinking, and the other at pattern recognition. As a result, we can feel two different things at a time. The corpus callosum which connects these two brain halves is, by the way, larger in women.
In certain ancient traditional psychologies engaged in teaching conscious evolution, the effect of all this was described as the cart the horse and the driver, that is to say, the physical man, the emotional man, and the thinking man, and that most all of humanity falls into categories based on the primacy of ones fit into 7 types based on this, with teaching that develop these capacities forming three well known methodologies, the way of the Fakir, thought the body, the way of the monk though emotion, and the way of the Yogi through the mind.
This is because beyond the cart the horse and the driver, is the self unknown to most,, referred to as the passenger, the one who knows where the other three are to go. We could say that the first three are machines and the last conscious understanding of function and form.
Each person born human with a capacity for empathy, is born whole and complete, but without any experience, in a non dualistic state. But because of the acquisition of language the unity of self is destroyed. The pain of being told one is worthless if one acts naturally as all children will, is too painful to consciously tolerate. A part of the self goes underground but some, call it a breathing tube to self love remains. Those for whom the experiences of childhood are merely traumatic and not overwhelmingly catastrophic preserve some deeply buried sense that life is good. For some there is so much hate and torture in their lives, the door is closed to any hope of love. A decision is forced to get even by making others suffer as oneself has. The capacity to empathize is preserved or lost depending on the degree of self hate. When the message is totally successful that one is evil one acts that way. One is totally convinced that one is worthless, not just carries that feeling hidden away. For most of us, it is only when certain buttons are pushed that the monster is released, the violence in the form of denial of memory that we were made to feel evil. When somebody points a finger, it threatens that within us. If we have preserved any sense of out inner goodness we do not want to feel evil. Sadly, will do evil to preserve our unconscious state.