What has been done has been done and there is no place for regrets. Facebook might (along with its partner and associates) be a big workplace but it definitely isn't the only launchpad for a happy & successful career.
He came a little bit snarky, true, but I yet have to see devstar who isn't snarky at least to some degree.
If this person is good, they will definitely have opportunities elsewhere.
That does not describe reality as I've lived it. I tell headhunters from Google, Apple, Amazon, FB and other huge companies to leave me alone every few years - seems like they expire their 'go away' notes after a while.
I've had zero problems finding quality employment.
It's an opportunity missed (it's a great place to have an internship or be a new grad, not so much for senior people who've worked elsewhere in industry) but the OP will certainly have no trouble applying again with some future recruiter.
Its not that he was factually wrong (or even wrong in etiquette) , but as my mom said you can be right and dead right, which is why he recognizes he needed a better approach to leave the most opportunities for his career going forward