Human beings are social animals, they are designed to live in small groups rather than anonymous large populations. Studies show that the individual is most happy with regular interaction with small intimate communities. The hormone oxytocin is behind the identification, bonding and relationships between people, and is the foundation upon which tribalism comes about.
As an individual I identify emotionally with the Left Hand Path, and I react strongly against anything that seeks to harm those of my tribal identification. These feelings I have of identification, and hostility towards that which threatens my tribe, is down to the impact of oxytocin.
A complaint about the ancient Welsh people was their constant infighting over land, power and wealth, in which they quite happily murdered their own brother and father. Yet, if an outsider killed their brother whom they had a quarrel with, the Welshman was quick to anger and determination to avenge the death through blood feud. Although oxytocin fails to keep brother from killing brother, it surges if an outsider kills the brother.
Interestingly, when the Satan Hunters, those promoting a Satanic Ritual Abuse fiction in London, had one of their number known as Rupert Wilson Quaintance IV jailed for nine months for stalking and harassing children and their families he considered were Satanists, the backlash was intense. Usually these Satan Hunters spend most of their time fighting each other, but as a tribe with shared values, the fall of one of their number resulted in a collective unified backlash against those they consider their enemy. The backlash is the result of the oxytocin hormone, the tribe pushing back against a situation that threatens them.
It is worth learning about oxytocin since it has a wide and significant impact on human history, society and reactivity.