Great quote.
Leonard Cohen's Anthem is about something similar:
Ah, the wars they will be fought again /
The holy dove, she will be caught again /
Bought and sold, and bought again /
The dove is never free
Ring the bells that still can ring /
Forget your perfect offering. /
There is a crack, a crack in everything /
That's how the light gets
George Martin quotes a William Faulkner all the time about fictional subject matter.
“The only thing worth writing about is the human heart in conflict with itself.”
It's why his fantasy stories have that gritty realism. The knights of Gondor riding against the evil horde of Sauron meme becomes parody. Good and evil is more subtle, cuts through the heart of every human being... regularly. The fantasy element is just about scale. It might be a choice between being kinda jerky and nice. Most people can be both. Novels get into a character's head. Stories where good and evil is a conflict within that head feel more real, because that's what it's like inside our heads.