You're assuming that people are a. searching for his book, and b. actually downloading it in the first place.
I would love to know how he is certain that piracy is affecting his bottom line. After all, he's hardly going to be able to get download figures from the piraters. Couldn't it be that nobody is reading it in the first place?
Yes, he has fallen into the classic "if people are downloading it, they must not be buying it, and thus I must be losing sales."
As we have discussed time and again, a download != a lost sale. The problem with that logic is that it assumes the downloader would have paid for it if it were not available for download. This is a false premise. As an example, for college, I am told that I need to buy expensive textbooks. If they are available for download, I will download them. Otherwise I simply don't purchase them.... ever. A download does not equal a lost sale in this case because I was simply never, ever, going to pay money for it.