The problem is not that the books are banned by some book stores. That situation is fine, and we can live with it. The problem is that access to those books is now significantly reduced. When a single entity gets too big or an entire industry chooses to ban something we have a problem. I don't know the solution but I do know this goes beyond a private company's right to sell only what they want. That right is now in competition with societies access to published works. It is also restricting authors and publishers from selling works that are legal to sell. This is a problem.
> The problem is that access to those books is now significantly reduced.
This is entirely false. The books can still be put up as an .epub at a URL on any of thousands of servers that can be accessed by the entirety of the internet-connected Earth. Such hosting service can be obtained in 5 minutes for a pittance, and will easily serve tens of millions. For slightly less than a pittance you can serve the file to billions.
If Facebook starts censoring posts or private person-to-person DMs with your URL in it, we have another discussion to have, but until that time this is just the normal freedom-of-association choices associated with being unpopular. Amazon sucks for doing this, to be sure, but the TFA is committing a worse offense: claiming inaccurately to have been banned.
There has never been a time where it has been easier or cheaper to publish to literally billions-with-a-b.
And what about when HN disappears the post talking about how Amazon disappeared the book you wrote? This thread is no longer accessible from the first (or second, or third, or...) page.