Like for a personal parallel, it would probably be wrong to announce to a friend that you thought they were ugly, no matter how correct you were.
The sincere apology would have been to announce that his answer was incorrect - otherwise he is just trying to pacify the mob, if that makes sense. Perhaps I'm being a little pedantic, but this email has clearly been proofread by a number of people, and the key statement is definitely not as clear-cut as this HN thread seems to be deciding (it's a very clear-cut non-statement).
Edit: Criticism definitely fair, I jumped to conclusions.