So, you didn't read the story? That specific line of reasoning was explicitly addressed.
From what I gathered of the story, Alonzo was trying to portray the inherent divisive prejudice of the phrase by altering the affected minority to one which is obvious(it's a lot easier to tell someone's skin colour than it is to tell their religion or lack thereof). You seem to be saying that since belief is a choice(which is itself arguable), it doesn't matter in this context. Would you feel the same way if the affected group were theists, or does that change the game? Please enlighten me if I misunderstand you(I just got off work, after all, so it's a very good possibility). As for if I misunderstood what Alonzo was trying to say, we could always ask him.