Lyric discussion by Miscfu 

Cover art for Empire (Let Them Sing) lyrics by Bring Me the Horizon

This song is definitely about Christianity. It's about how God turns his face to people who don't accept him.

I hear them clawing at the gates "Let us in, let us in" I hear them calling out my name (I don't care)

I think it's pretty obvious this is the gates of heaven. The people who want in are people who died not believing in him. And the whole part about "let them sing" is stressing that God just doesn't care what they say.

"The blood on my hands covered the holes" Another remark about Christianity. Oli is saying he's a "sinner"

I think the whole purpose of this song is to point out how stubborn Christianity is and question the believability of an elitist religion (ex. "we're all sinners, but only people who believe in God can get into heaven).