Negative Love of self means separation from others and is different from true self-love from a unity perspective (loving yourself and everyone else), therefore separating itself from the Oneness of the Creator.
The polarity is dependent on the closeness to the Creator with negative polarity being furhter away and positive polarity being closer to him. Even in the fifth dimension the amount of negativity is so low it's negligible.
The source of evil is another story and a whole other rabbit hole.
Cobra said it's a "primary anomaly", a quantum random function without a pupose that forms the basis of evil, but is not evil itself.