It's more useful than that. The story about smallpox-infected blankets has been around for a long time and a lot of people believed it. It's good that it is being debunked.
Also, this makes a case that Churchill is not only an offensive anti-American lunatic, but also a fraud. As other posters have pointed out, academia will tolerate offensive opinions from the left but take a very dim view of academic fraud. So this will turn people against him who might have been in his corner before.
Like any of us needed to be told that here on FR? Preaching to the choir - I for one don't want to increase his speaking fees by turning him into a counter culture free speach martyr - ignoring is sometimes the best punishment.