I don't think it's fair to say this comment is 'wrecking DDG's carefully built up reputation'. If what he describes is damaging their reputation to you, that's on the business, not on the commenter. If anything, the commenter seems to have been honest and straightforward with what's going on.
Sounds like you'd prefer him to have run a message past management/public relations first?
If you speak in a public form in response to something that seems damaging to the reputation of the company in a way that is probably even more damaging to the reputation of that company you are either an official spokesperson or way out of your depth. Pointing that out is a service, not a sleight. And yes, if this is not in an official capacity he should either keep quiet or run it by the PR dept. People have lost their jobs for far less. Anyway, I've pinged @yegg, hopefully he can shine some light on this.
Sounds like you'd prefer him to have run a message past management/public relations first?