Not to interfere with any internal screaming, but I think (hope?) most would agree that a secondary elephant in the room is that suppressing knowledge so as not to help the "bad guys" tends to be the worse evil.

I don't see how that applies in this case. This is just someone saying hey bad guy, here is an idea on how to perform your dastardly act "better."

Having this public doesn't really defend against it any way. And if someone were to perform this act, it would be easy enough to figure out what was going on.

I think it's fine to publicise better attack methods, so we can figure out how to defend against the next potential version.

We should be moving to better solutions regardless, like append-only backups.

I believe it applies, as someone who doesn't know much about crypto AND is interested in protecting myself, this small tidbit of information moves me closer to being an aware and self-defensive computer user.

Any bad guys with sufficient ambition and intelligence are going to get as far as they're going to get, and if you're afraid of talking in public because a "bad guy" might overhear you and become smarter, you really are living on the wrong side of matters.

The knowledge he is writing is so basic anyone must understand.

You're saying like "We should not teach programming publicly since bad guy may misuse the knowledge."

This is different. He I specifically addressing what the bad guys should do. If he talked in more technical terms without spelling out what the bad guys should do, your argument would be legitimate.