Is Amazon going to deplatform Ann Coulter or Bill O'Reilly because they don't agree with their ideas? Are they going to pick-and-choose which books are allowed rather than sell what the market wants? How can we deconstruct or debate what you or I think is terrible writing if we can't access or purchase it?
The argument that businesses can sell whatever they want falls away when they become monopolies and gate-keep much of everyday life ubiquitously, influence (corrupt) government policy extensively, and can shut people and products out arbitrarily; that's inverted totalitarianism. The common tendency to deny the absurd power of megacorporations to influence attitudes and pick winners and losers is itself absurd.
Edit: Regardless of content, I hope such books are available on other platforms and use their banning as a cause celebre to defenestrate commercial censorship. Also, maybe I shouldn't buy products from such a platform in protest if they're going to Big Mother customers.
"'I disapprove of what you say, but I will defend to the death your right to say it,' was [Voltaire's] attitude now." - Evelyn Beatrice Hall