I'm not sure what you're arguing here. Unless you know that the Parler/Amazon contract included a cure period, the specificity of that period, that Amazon hadn't notified Parler of contract violations previously (i.e., so they extended past the cure period), and also included no other relevant termination clauses (including termination for convenience), then we simply can't say that Amazon breached the agreement despite Parler removing content. There are a myriad of ways they could have fulfilled the agreement, and/or Parler breached the agreement with Amazon.

Please, separate legal arguments from emotional arguments. I'm strictly speaking legally.

Regarding Facebook, the choice to enforce, or not to enforce, a contract term is exclusively the right of the parties to the contract. Amazon may have unfairly chosen to enforce contract terms against Parler and not enforce those same terms against Facebook (for example; though I don't believe Messenger is hosted on AWS).

That's completely irrelevant; so far as I know, no law says all parties to all contracts must be treated equitably.

You will have a compelling argument when and if law enforcement chooses to crack down on child porn on Parler but not on Messenger. In this case though, you're comparing apples to baseballs: their similarities are vastly outweighed by their differences.