At a quick glance it looks like a public forum (which has a bearing on how I view the ethics of the situation although even if it was private I don't think DO should act). When you are asked a question about your employer in public you are speaking for them and if you say something dumb that your company doesn't like that is your action and responsibility not someone who reports it. When I worked for a large company I used to speak (and particularly write online) very carefully except when truly in private. I also don't see any reference to anything being "off the record" so I don't see why you assume it wasn't "on the record".
Would I write that article like that? No. Do I think DO should claim editorial control over it? Hell no.
Maybe DO could request the blog owner provide contact details (I can't see any on the current site) so that legal action could be brought directly against them as the publisher rather than against DO. Not offering such may be reasonable grounds to have DO demand editorial changes or cease service.