That doesn't feel legal. They're blatantly using their market position to suppress competition for the sole purpose of suppressing competition.
Fuck Facebook as much as them, but if you're going to cheat that hard you're supposed to at least give yourself some kind of plausible deniability, like Google's "we're not trying to monopolize spying on users; we're trying to protect user privacy and prevent bots from harassing websites" to push their DRM shit.