From tptacek's comment, it sounds like the author of the book may just be an inexperienced practitioner of cryptography who's only crime is to be too eager to spread what they've learned.

Someone who picked up the basics from a few Wikipedia articles here, a few papers there, a couple open source projects here and there... they're smart, so they're not completely clueless about the field, but they just don't have the experience to see where they fall short, the industry know-how, and so on.

I feel like instances of this in the tech community are not too rare, and it's a consequence of the internet: anyone can publish a book and distribute it all over the world now. It's worth keeping in mind that while harm is being done through the spread of false information, what's most important is to educate them, see this as a teachable moment, so they can become productive experts and modify their message to be fully correct. Of course, it requires them to be open minded of their shortcomings: but it can be done.

PS: I have no clue who the author of Practical Cryptography With Go is.