When you've got some kind of duty [in the legal sense] towards the person sending the mail. For example a doctor quoting a patient's email would be problematic. Just to be clear, I don't know the law in this area and I'm not saying what he did was illegal (I have no idea), I'm just saying that I can certainly see why NYU wouldn't want to step up to defend him on this issue if something came up.
I'm not sure how you can consider doctor/patient and professor/cheating student the same type of relationship. Hell, this was a 100-level class; it's surprising it even had a professor.
Aside: I saw a geek news bit about you withdrawing (removing) your post and the heat you're getting.
Dude, I'm so sorry.
For future, I have two bits of advice.
#1 Don't bury the lead. Like myself, the geek news bit also didn't get the point of your post.
#2 Focus on the positive. Meaning that all negatives can be stated as a positive.
So, were I to have written your blog post, I would have lead with your "future" section (peer reviews, competitions, contemporary projects), enthused about all the positives, and underplayed (or flat out omitted) the back story, the bullshit plagiarism software, the complicity of the administration (shocker!), the cheating students, etc.
I definitely would not have responded directly to any personal criticism, especially not in public. That's always a trap.
In conclusion, I think you did the right thing, are on the right track, and got burned by being the internet's chew toy of the moment. Lesson learned, move on.
the post was supposed to be "a story with the twist." Had I known that I was going to have hundreds of thousands of people reading the post, I would have followed the standard journalistic practice of writing a summary at the very first section. (See http://t.co/2kJEkJW for a copy of the post. Note: I asked the post to be taken down until I repost the original article but the journalist is really playing childish games.)
I kind of felt this a few hours after the post went out, so I added two clarification points early on in the article:
1. I am not giving up the fight, I will just fight differently, please see the conclusions (link),
2. This was not about NYU and people cheating in business schools; people cheat everywhere: the story gives an explanation why they remain undetected.
Oh well, people could not even read these two points.
But I want to write stories in my blog, not papers with an abstract, executive summary and table of contents.