The Dangers of Microsoft Pluton

I'm completely missing how his example of a Word document that can only be opened by approved users on approved hardware within the corporation is supposed to be a bad thing.

Honestly, that sounds pretty fantastic. I've been using 3rd party tools/extensions to do this sort of thing in corporate and government environments for years, but having the attestation go all the way down to the hardware level is a big value-add, especially with so much ransomware/spyware/extortion/espionage going on these days.

Can someone please explain to me how the author might see this level of security as a bad thing?

what's stopping someone from taking photos of your precious document and posting them on 4chan?

nothing. there's nothing you can do to stop that.

Try to scan banknotes with a scanner and you will see.