Companies can't honestly investigate themselves.
President Nixon would have liked to investigate himself, as would the tobacco companies. Every other organization would like to interview their personnel then go out and give their version of what happened.
Commissioner Roger Goodell is in a no-win situation. He has said over and over that his job is to protect the shield.
With that being said, how can he then dig into the Spygate controversy and pull out dirt that will damage the shield.
A lot of sportswriters who question everything everybody else says, trusts the NFL and everything they say, even when telling the truth might not be in their best interests.