Why Narcissists Hate

The reason the Narcissist "hates" a person is because they think the person made them feel badly.
People with Narcissism (not necessarily all sociopaths, not necessarily all psychopaths) typically live life through their egos, and don't know it. So when something happens that causes them to feel any "negative" feeling, or when they feel embarrassed because they feel caught or accused, their "negative" feelings trigger defensive rage.
Not unlike many very young children.

When they feel anything "negative", they look immediately for something external, outside of themselves, to blame. It can't be themselves, because that would mean they are not impermeable, and not perfect, and not "above" others. Even if no one knew they accepted responsibility for something "wrong", THEY would know, and they would have to pass it through their ego. Since they've made their ego into a solid shield, any responsibility they try to take for their own actions or feelings bounces off, it can't get in. It's a barrier against even themselves.

They can dismantle it from the inside, but they would need the "key", and in order for them to get the "key" they would first need to understand that they've turned their ego into a shield in the first place, and that would mean feeling like they did something "wrong". Conundrum. Irony.

Since that's been their protection for so long, they may not want to entertain the thought, at all, of dismantling it. Only they can do it, another person can't make them. It's their free will.

Their shield protects them from feeling real things, especially guilt, remorse, regret, loss, and shame, and fear.

In most cases, at some point in their lives, or several points, those feelings were associated with terrible humiliation, abandonment, terror, and/or physical abuse. Their young minds looked around for people who did not seem to receive consequences from other people, who appeared to live "above" the reproach of others, who were for some reason apparently on a higher rung among humans.

That's who they wanted to become, one of the people who didn't get humiliated or attacked, so they emulated them in every way possible, mimicked them as much as they could. They knew that if they BECAME one of those people, and then if they were ACCEPTED by those people, and especially if others FEARED them enough to believe that they were a "BOSS PERSON", they would never need to be afraid of those feelings again.

And they would get everything those people got: "Respect", admiration, positions of control and power over others, service from others, sympathy from others, praise and applause from others, "LOVE" from others (what they think is love).

Since a person with Narcissism did not learn how to make respectful, healthy, polite connections with others, how a relationship is built and what it's built WITH, they did not learn that demanding love or loyalty is a futile exercise and only serves to push people away.

Since a person with Narcissism did not learn that there is no such thing as "the better people" and "the lower people", just like there's no Easter Bunny, they cling to the fantasy that they are one of the "better people", and they constantly categorize and recategorize others to be in one group or the other, so their relationships are based on whether they've categorized a person in the "better people" group or the "lower people" group, and that can change from day to day. They don't know it's not a real thing (like the Easter Bunny).

A lot of children go through stages of what appears to be "Narcissism", but adults who end up with traits of the disorder did not mature past those stages for one reason or another. People can get "stuck" in childhood developmental stages for many reasons, most often from trauma of some kind.

Sometimes trauma doesn't look like trauma at all.