It's hard to explain beyond a gut sense of this, but I would worry more about google.social than facebook.social in the fediverse.
But I would vehemently oppose any moves to pre-block new servers just on the grounds that they might be bad.
And I would welcome the opportunity to leave Facebook entirely if I could connect -- via Mastodon or whatever ActivityPub tool I use -- to the people there whose social media world starts and stops on that site.