I think it's important for people to realize that facebook is completely within their rights
Yes, it's within their rights, so it may be legal, but...
however, there is nothing illegal or unethical about them doing so.
How does this imply that it not being unethical? There are certainly plenty of cases where something is "within your rights" and "legal", but still unethical. If I plagiarize an out-of-copyright author, what I'm doing is unethical, but it's still within my rights, as wrong as it is.
Let's not perpetuate this stupid "it's legal, so it's okay" meme: not all things which are "legal" are perfectly ethical, nor are all things which are not "legal" unethical.