A new ethical universe

This is a re-post from the BBC College of Journalism 'Discussion on CoJo' pages.
*** UPDATE: Kurt Greenbaum's response here. ***
Kurt Greenbaum is the director of social media for the St Louis Post-Dispatch. He blogs on his own account as well as running a sector of the newspaper's website - stltoday.com.
On Monday, 16 November, Kurt posted this article both to his blog and to 'The Editor's Desk' - one of the parts of the website for which he's editorially responsible.
It told the story of a reader who'd posted a one-word response to an earlier blog which asked the question "what's the craziest thing you've ever eaten?" That word was obscene and would certainly have been removed by any moderator of any responsible blog - which is precisely what happened.
But it didn't stop there. Kurt takes up the story himself:

"A few minutes later, the same guy posted the same single-word comment again. I deleted it, but noticed ... that his comment had come from an IP address at a local school. So I called the school. They were happy to have me forward the email, though I wasn't sure what they'd be able to do with the meagre information it included.
About six hours later, I heard from the school's headmaster. The school's IT director took a shine to the challenge. Long story short: using the time-frame of the comments, our website location and the IP addresses ... he tracked it back to a specific computer. The headmaster confronted the employee, who resigned on the spot."

Kurt's actions have not gone down too well with his blog's readers. At the last count, there were 152 entries, most of them condemning what he did - some in strong terms, including phrases such as "thought nazi".
Sentiments such as this from 'Andrew' are more reasoned and catch the tenor of the responses:

"That was a really low move. The Post-Dispatch opens up their message boards to all users and takes it upon themselves to self-police them. Retaliatory attacks against users is not something that any person should expect from using these boards, save for threats of bodily harm or death."

What seems to have got up the noses of most of his readers is Kurt's tone in both telling this story in the first place and subsequently defending it where, in message board posts, he urges reader/writers to "follow the rules" and then they'll be OK.
So here's an ethical question journalists have never had to confront before. Is removing obscene or offensive comments in moderation enough? Is banning users from future posts enough? This offensive comment was posted from what appeared to be a school computer - does that change the ethical issues involved?
Should a message board poster risk losing his or her job for a comment which, though offensive and obscene, is neither illegal nor threatening?
I've emailed Kurt to ask if he's had a chance to reflect on all of this yet - I'll let you know what he says.