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But it is decidedly legal to publish materials that explain how to do so.

Are you sure about that? https://en.wikipedia.org/wiki/Illegal_prime

Kicking someone in the face is illegal too, but there a million - or more - YouTube videos showing you how to do it, and most towns in my country have more than one class you can go to to learn how to do it (TKD, BJJ, Karate, etc.).

"Well you can use it for defence ..."

White-hat hackers are a thing too.

No one here mentioned DRM, though that would be a valid subset of videos to delist under this new rule.

What if I want to reverse engineer my toaster, and make a video about it?

I'm sure there's a way the toaster company can interpret your video as a copyright or trademark infringement.

If you could figure out the order of construction of the parts in the toaster that could be considered intellectual property/trade secret.