I hardly think getting blacklisted by FB would lose you opportunities outside of FB. Sure, you probably can't get a job at Instagram because they probably share the recruiting database. Beyond that, there are a million startups, and tons of other medium and large engineering companies that need technical people. Seriously, Apple, Google, Microsoft, etc are all trying to steal each other's employees. They are competing so they definitely don't share such information.

If this person is good, they will definitely have opportunities elsewhere.