Sorry, that I am coming to this thread two weeks late, I just noticed it, but anyway ...
The original argument is just wrong. Amazon does not threaten freedom of expression. If you do not want to use Amazon you can start your own web site and sell or give away your book. No one will censor you or stop you from saying whatever you wish.
Now, it is true that Amazon has huge market power. For the small guy, if you want to sell on Amazon there is no negotiation. You have to accept Amazon's terms and conditions (including pricing rules). Since the Kindle has such a large market share, most people want to sell on Amazon and have to agree to those terms.
But a claim that Amazon is censoring you? Amazon accepts almost anything as long as you agree to their terms.
If this bothers you start up
www.altPub.ink (its available!) and invite all of your like-minded author friends to join you. There are very few barriers to entry. Use calibre and you can even sell your books in Kindle-compatible format.