Well, it's a good thing you're not a lawyer then!

By analogy, if the original comment had been "I will not give you a copy of the copyrighted harry potter book, but I can teach you how to use a scanner if you'd like, and I'm sure someone else will scan it" would you say that teaching someone to use a scanner is illegal?

It's actually typically legal to make a backup of a copyrighted item you own for personal use if the original is damaged.

He's teaching people to do something that's typically legal, avoiding infringing copyright by redistributing himself, and commenting that it's quite likely others won't be so scrupulous; I don't see how anyone could reasonably fault him.

There's an active hobbyist lockpicking community out there with plenty of instructional videos. One could nefariously apply these skills, doesn't make the video producers liable.