Why couldn't you simply respect the author's wish to leave the text private?
I've been in a similar position, saying something incendiary on a large corporation's public intranet comment section. What I said was more objective and pointing to a specific instance that was very fair to criticize and ultimately damaging to the company, but the next day I was well aware the cat was out of the bag I needed to defend my position with logic and reason and not try and hide it. In fact I emailed my manager immediately the next morning, saying that I was worried about the blowback and linking to the comment. I feel for the author, because the anxiety was definitely a ohh shit moment. Looking back, I probably shouldn't have made the public comment in the first place because it was emotionally driven and it did hurt my advancement.
I wanted to read what the author wrote.
https://web.archive.org/web/20220523144108/https://blog.derh...
But I still disagree with you not respecting the author's implicit wish. For instance, thanks to the various similar links like the one you just sent, I can pin-point exactly who the person in question is. How can you guarantee the information will not be used against the person? I'm not sure if this is on your ethical framework to consider, but that's where I see the fundamental disagreement.
You could have privately read the text (because you know how to access it), while not posting the text per-se here, and you could even comment something insightful about it. It is more about the anthropological aspect of it, the respect of privacy, not about the technical aspects of the public town-square that the Internet is.
Clearly the author did not know any of these either, nor about what a PhD actually entails. But still, these are mistakes that can be part of someone's life.