That’s a great question.
The short answer is no, Facebook doesn’t have the right.
The original content creator has not agreed to Facebook’s ToS for their content. So the person posting onto Facebook cannot grant Facebook any rights as they don't have those rights to grant in the first place. The person posting the content would be in breach of Facebook ToS by posting content they do not own or have permission to post.
It would be like trying to give away your neighbour’s dog. You might tell the person you give it to that you are able to give it to him, but if your neighbour sued the new owner to get his dog back, the new owner would have no right to keep it.