If you used "defense of mass incarceration" in the spirit of the HN guidelines, i.e. because you thought it would make for an accurate and neutral title, then we definitely misread your intention and I'm sorry.
But I still think that title was a mistake. "Mass incarceration" has become a pejorative that signals a certain position (or cluster of positions) on this controversial issue, so saying "defends mass incarceration" comes across as a provocative critique, a la "defends wife-beating". For a really neutral title, maybe "FBI director's speech defending current prison policy" or some such would have worked—assuming that's what the speech actually is.
Certainly the title we hastily gave it wasn't great, except as a cooler-offer. It's actually rare for an article to be quite so unhelpful at indicating what a good title for itself might be.
There's a standing invitation, btw, for any HN user to suggest a better title if they don't like the one that's up there. When people do, we often use them.
I do know it was being strongly upvoted under this title, which might be objective proof of linkbaitiness...