Anyone can sell the book themselves. Routinely you will see people on HN self publishing technical titles on Leanpub etc. No one is shouting them down or deplatforming them.

Amazon is a private company and they can sell what they want. That seems to bother you, because of a de facto monopoly they hold, but that is beside the point. Why do you think it is an author’s right to have any third party sell their book?