In the course of history there has been oppression. Oppression comes from hate.
Hate creates darkness in men's souls.
Hate cannot drive out hate, only love can do that. The darkness and hat Dr. King speaks of are metaphors for injustice and oppression. I grew up in an area where I was the minority. I was the one who was singled out for being different. I know first hand the darkness and hate Dr. King speaks of.