"Leave Black Catholics out of it."

You are shifting the meaning of the metaphor. That metaphor has nothing to do with the color of one's skin, much less one's religion. "Brown priests" of Nazi Germany were black-hearted to compromise the Gospel as are Imams today in the Middle East who exploit the tensions there to attack everything about the West. Nancy is just as black-hearted, making sub-textually the sins and crimes of a few intrinsic to the faith-integrity of everyone in the church. Maybe a better metaphor for Nancy would have been "white-fanged" to best express the center and excess of her anger. 
As for you -- Raymond J. Jirran, Ph.D. -- you need to go back to English 101 and attempt to acquire a literate knowledge of metaphor. A metaphor like an big onion should have successive peelings of meaning. Not one! No doubt when W. Stevens says "a man and a woman and blackbird are one" you conjure up images of miscegenation. Or think a black hole is some kind of black ghetto. Sad.