You think the Fediverse is free? You do know it takes labor to develop, right? You know servers aren't free, right?

And anyway, privacy isn't the issue. Consent is. Public writings are by default not private.

But since you ignored the very prescient example of the argument used by rapists, here's another one that shouldn't make you balk and dismiss out of hand:

First, suspend the legality of this analogy. We're discussing logic, not law. Next, pretend I take your phone that you left on a coffee shop table. You say, "That's wrong. Give it back." I say, "You didn't expressly say I can't take it, and it's sitting there in public, therefore I can take it." It doesn't follow that I can take it just because you didn't explicitly shout out to the other patrons, "Don't take my phone!"

It's the same with anything you put out in a public forum. Leaving it there isn't implicit consent to use for someone else's gain.