How much does it hurt the supermarket if I just walk out with one bag of shopping? I mean really, it doesn't hurt them at all. Are you saying that should also be legal?They didn't do anything that hurts Apple. They received a developer unit, then posted a teardown. They likely reassembled it and it probably still works fine, so I doubt they "destroyed" something they were given for free to show the teardown.
If this had been a free pre-release iPhone and they had filmed drop tests and other obvious things to show they only got it to destroy it and not to use it for development, that would be different. But all they did was take it apart and snap some photos.
I believe strongly in the mantra of "If an activity doesn't hurt anyone, it shouldn't be disallowed."
They received the developer preview AppleTV with an attached NDA (that's a legally binding agreement) and they broke it.
They knew they were breaking it and decided to do it anyway.