It's possible that, in this situation, everyone is a little bit right and a little bit wrong.
I think that, in general, Forbes is onto something when talking about how the hardcore gaming press handles certain highly-publicized properties. It's difficult for those games to receive real criticism, either in the leadup or come release time. But when they get factual errors wrong while writing about this thesis (be it in the GI cover story article or in the lazy bit about Gerstmann), they look like pretty crappy journalists.
Why shouldn't Matt Helgeson be pissed, if someone is posting factually false information about his publication? If you're going to make inflammatory claims about the integrity of others, you have a responsibility to actually back them up. If it's that self-evident, it should be trivial to find proof. In a way, his tweets show enough to build a case on (what does it mean to "work hard" to get an exclusive?). There's no need to overreach.
Also, I think it's hard to deny that gamers have done about as much to build this echo chamber as the publishers and journalists. The shitfit thrown over the Uncharted 3 Eurogamer review is evidence enough of that. There's an audience that wants a real dialogue of game criticism, but there are at least as many people (if not more!) who want someone to tell them what they want to hear about games they either anticipate or enjoy.
I'm glad Forbes is starting this conversation, because it's pretty overdue, but it's not like they're beyond reproach.