Natasha explained to Pilerats what the song is about:
"There’s a song called Never Forgive The Angels which is very angry and I think it’s really important not to get rid of one thing or the other, but you have to go through it and, like you explained, you had to go through those things and let out those emotions and sit with that. Spitefulness or anger or resentment kind of contort things and create monsters out of people, because that’s storytelling too and the human experience and I think that can create great works and great villains and great dark sides, and we wouldn’t have Star Wars if we didn’t have the villain."
Natasha explained to Pilerats what the song is about:
"There’s a song called Never Forgive The Angels which is very angry and I think it’s really important not to get rid of one thing or the other, but you have to go through it and, like you explained, you had to go through those things and let out those emotions and sit with that. Spitefulness or anger or resentment kind of contort things and create monsters out of people, because that’s storytelling too and the human experience and I think that can create great works and great villains and great dark sides, and we wouldn’t have Star Wars if we didn’t have the villain."
Source: http://pilerats.com/written/get-to-know/bat-for-lashes/