Once upon a time, you could pretty easily get away with a blanket statement like that, and have it come across as wise and all-knowing. But today, in the day of The Internets, it's a wee-bit trickier.
And so it was that Chad Flanders, a law professor at Saint Louis University, decided to look into Justice Scalia's claim and did research. What he found was that, indeed, the concept of "racial entitlement" had indeed been written about. But only one time substantively. All other few mentions seem to stem from that one time.
But okay, it did get written about, if only one time. It was a "little known article" from 34 years ago, in 1979, titled "The Disease as Cure."
So...who wrote that one, lone article about "racial entitlement" that Justice Antonin Scalia used as evidence that "racial entitlement" had, in fact, been "written about"?
The author was Antonin Scalia.
That's the equivalent of you telling someone that Joe is a rat-bastard liar, and then going around saying to everyone you meet that "Y'know, people are talking about how Joe is a rat-bastard liar."
And then using that as justification for changing the law of the land.
By the way, just to be clear, just people something has been "written about" doesn't inherently make it defensible, even if it hadn't been Justice Scalia who said it. I suspect you could find any pig-headed, offensive, racist, reprehensible thing "written about" somewhere on the Internet. So, being "written about" isn't a big deal in the slightest. It's who wrote it. It's what the source is. It's how widely it's been "written about" and how substantively. And that's just the starting point. Because, in a perfect world, it's good also to know what the refutation might be that's been "written about."
But I wouldn't necessarily expect Antonin Scalia to know about this. Or be fair about it. He's only a Supreme Court Justice.