I'm an author myself, so I certainly don't dismiss his concerns lightly, I just think he's overthinking it. It's like stressing out over used book sales or people borrowing the book from the library or a friend. Most of the people buying used copies or borrowing would not have bought the book anyway. Are you going to not sell your books to libraries, or forbid used booksellers from selling it? Good luck with that! I maintain that a lot of the people who downloaded it on the darknet not only would not have bought the book, likely they will never read it. They are collectors.
I see that a lot on the needlework lists and forums. I can't tell you how many times I posted "I made a scarf out of really nice yarn" or something like that and received several e-mails demanding the pattern. You need a pattern for a scarf? It's a giant rectangle. Figure it out.
I usually make up that kind of thing, and use interesting stitches or pretty yarn, and that's what makes it interesting. But they MUST HAVE EVERY PATTERN. There's a site that offers (or used to offer) a free crochet pattern every day, which goes away at midnight and is replaced by a new pattern. If they miss downloading one day's pattern, they're on the list having a nervous breakdown, and trying all kinds of underhanded ways to get someone to give it to them (the listmods don't allow discussion of distribution of copyrighted patterns). Nobody can make a new item every day, and a lot of them are free for a reason (because no one would buy a pattern for such a fugly useless thing), so there's no reason to be upset over it. But they MUST HAVE EVERY PATTERN. It's a form of OCD, I guess. I think a lot of darknet e-book collectors operate from the same place. I do it myself a bit with the free books here at MobileRead. I'll see a book that looks interesting and I download it and I have no idea when or if I'll get to it, but maybe I will someday, and there is plenty of room on my SD card, so why not?
So my point (and I do have one) is that there's no use stressing over illegal downloads too much, because the sales you lose are infinitesimal compared to the bad will you will engender with actual readers if you treat them like criminals by locking up your ebooks with restrictive DRM. I'd rather see authors turning their energies to finding a better solution. I'm not sure what it is, but complaining about a tiny minority snatching the bread from your mouth is not it.