I strongly believe that privacy is important, but I also think that it is important for people to have clear expectations of when they can expect it.

Is it so absurd to say that if I post stuff publically I cannot expect it to be private and if I post stuff privately I should absolutely be able to depend on it to be private?

I think your example of parler is an example of a service that was not adequately secured to protect it's private communications and the facebook example is clearly unethical and just one of the reasons I don't use the service.