Black magic can be liberating if you have been brought up in an excessively narrow moral code, and have internalized it: bought into it. According to a rigid morality, everything is black and white, and there is no freedom. This is the logic of eternalism: if there is single source of meaning in the world, you had better do what it says.
Fundamentalist religion does this, and black magicians often grew up in repressive Christian households. But black magic might also be a way to escape childhood indoctrination with political correctness. That is also a fundamentalist ideology, although not quite religious.
Brought up in fundamentalism, part of you becomes an internal tyrant, who punishes any deviation from the code. The tyrant views the part of you that resists as a monster. This internal war may be intensely painful and destructive.
The best way to bring peace is gradually, “eating the shadow” bite by bite. In “We are all monsters,” I described this as the strategy of incorporation: recognizing the monster and the tyrant both as aspects of yourself. In fact, they are not “parts” at all; they are ways of being, that you can enter into or drop at will.
If the tyrant is exceptionally brutal, the gradual approach might be impossible. The only way forward may be violent revolution. You identify with the monster, and murder the tyrant. I called this the strategy of inversion.