What, then, is the coded meaning of 'You are so nineteenth-century' in the context of an argument about religion? It is code for: 'You are so crude and unsubtle, how could you be so insensitive and ill-mannered as to ask me a direct, point-blank question like "Do you believe in miracles?" or "Do you believe Jesus was born of a virgin?" Don't you know that in polite society we don't ask such questions? That sort of question went out in the nineteenth century.' But think about why it is impolite to ask such direct, factual questions of religious people today. It is because it is embarrassing! But it is the answer that is embarrassing, if it is yes.
The nineteenth century connection is now clear. The nineteenth century is the last time when it was possible for an educated person to admit to believing in miracles like the virgin birth without embarrassment. When pressed, many educated Christians today are too loyal to deny the virgin birth and the resurrection. But it embarrasses them because their rational minds know it is absurd, so they would much rather not be asked. Hence, if somebody like me insists on asking the question, it is I who am accused of being 'nineteenth century.' It is really quite funny when you think about it. (The God Delusion, p. 157-157)