I think it's pretty safe to say that the majority of us are here to avoid another corporate takeover of our preferred platforms. It would seem to me to be a tad irresponsible to allow Facebook into our space with open arms, allowing them to hoover up our data. I would love to keep using Lemmy.world, but will happily change instances if need be, and I feel many share that sentiment.
Hate to break it to you, but the fediverse is public. Most instances don't even require an account for read-only access. If Facebook wants your data they don't need to federate to get it.