a) Parler is hardly being “kicked off the entire internet.” They are being severely ostracized and being denied service by major online companies. This would happen to me in my city’s various bars if I developed a reputation as a violent drunk - it is not a violation of any fundamental liberties. Regardless, the idea that Parler can’t exist without AWS is ridiculous - what is true is that maybe you shouldn’t use AWS to run a business that makes money hosting Nazi propaganda! In general people should be aware of the risks of offsourcing to the cloud... especially when your business model is odious and immoral.
b) Parler is not some innocent social media service that got overrun with Nazis. While its leadership is secretive, it is heavily financed and owned by major conservative activists, and a great deal of its marketing is towards disaffected far-right Twitter users.
c) Again and again and again: nobody has ever complained about YouTube banning pornography. It is not because we’re moral scolds who want to make porn illegal - it is because pornography is a shady business with shady people and YouTube has every right to not want to get involved with it. It would be a violation of the first amendment to force YouTube to host porn. Likewise it would be unconstitutional to force Twitter to restore access to @realDonaldTrump. The exact same applies to AWS or the Google App store and hosting Nazis on Parler.
This grotesque perversion of “free speech” being used to shield people from the consequences of hate speech is one of the more worrying ideological developments in recent years.