I wonder whose side the FSF would take.
Amazon shouldn't be making these decisions, and certainly not without giving the other party ample time to make other arrangements. This should have been litigated in court prior to taking deplatforming actions.
Imagine if Amazon was a Chinese company and Parler hosted information about the plight of the Uyghur people.
Community websites have the right to enforce rules. I'm not so sure common carriers do, and AWS is a common carrier. A good rule of thumb for American hosting companies is if the FBI won't seize the website for the content hosted therein, the website shouldn't be removed.
For context, I'm a liberal and dislike the content on Parler. Defending free speech is more important than zapping the republicans. Imagine if the tables were flipped and talking about abortion was what conservatives wanted to ban.