When others try to influence what we can and cannot read, that is censorship. Period. If it affects Amazon's ability to sell its product, that is also a form of censorship, too. Amazon should stand up to this kind of thing; as an author, it sends chills down my spine.
As a consumer, I find it depressing. A free and open market is where you decide not to buy if you don't like a product, not force it out of the marketplace because you and a group of your friends don't like it.