Haha, well at least Tolkien wasn't Ann Radcliffe. With all due respect to the true mistress of the pseudo-Gothic novel: her
Mysteries of Udolpho was set in the 1500's, yet she wrote of Italians drinking coffee in cafes in Venice in that novel.
Mistakes happen to everyone. Some can be quite funny, actually. The Barad-dur references cracked me up originally. I guess I tried to imagine it...