Amazon has no power over whether or not you buy it. They only decide whether or not they sell it. If you want to contact the author or publisher or another bookseller and purchase it, please explain how Amazon is preventing you from doing that?

Fine, so buy it somewhere else. Better think long and hard about the legalities of giving anyone bleach to drink, though.

But you don't get to decide whether mixing bleach into your kids' Yoo-Hoo is in their best interest. Because it empirically isn't. A parent who tried to do this would be justifiably arrested on child endangerment charges, and no amount of "parents' rights" kvetching would negate that. And if some parent went on to write a book boosting this idea, Amazon would be roundly condemned if it knowingly allowed that book to be sold on its platform.