Facebook is a major component of the return of fascism in the United States. Arguing for allowing them to federate is like arguing for ISIS to be part of the fediverse.
No. This isn't the matter of making a choice. This is a matter of ensuring that outright poison isn't allowed into one's system.
They DO have free choice to choose. Just as the site is free to choose who they list and what criteria they use for such. They’re not entitled to get listed if they don’t align with the site’s policies.
Choices doesn’t mean free from consequences or entitled to anything you want.