Parler has users who are actively trying to overthrow the government, after their first and failed attempt 3 days ago. It's become their safe space because they have already been banned on other platforms for months/years now. This situation is vastly more unique and organized then the standard hate speech that appears on every other platform (and gets removed when caught or amplified). This is ISIS level radicalization in the United States.
By banning them you only move them more and more underground. You will end up making them go to Tor and organize in a place where no one can observe them. But these people can feel free to continue shooting themselves in the foot. There is a reason 4chan is allowed to exist.
Moving them underground to limit their radicalization of every day people seems fair. Law enforcement's role is to infiltrate, observe, and prosecute when necessary.
Parler did nothing to prevent users from organizing insurrection and violence (and succeeding). Twitter flags posts and suspends/bans users who violate their TOS.
You know damn well Parler only exists because their users were already banned/flagged from Twitter and needed a safe space for their hate and radicalization.
To add to that on the OP's comment, YouTube (Google) and Facebook use their own resources and self-host on their own infrastructure.
Additionally, you will also soon realise why Google and Facebook are essentially THE internet, since they themselves are domain registrars and are both part of the ICANN.
So it is almost impossible for them to be 'taken down'.
Putting aside the fact that I have no clue what you mean when you say "YouTube and FaceBook's compute resources on AWS" (Google and Facebook have their own datacenters), Google and Facebook have robust content moderation policies/procedures. That alone explains why "the same pretenses" wouldn't apply.
