First, he points out that other organizations, with many times more members, would never get live coverage of a press conference, let alone from three networks. While correct, the media was not just covering a newsworthy event. They were also chronicling the beginning of the end for a very powerful group in America politics. The NRA's response to the Sandy Hook shooting was its chance to redeem itself in the eyes of Americans who blame it for our recent mass shootings. They failed. The media wanted to be there to watch it.
The link to Lawrence O'Donnell's comments is here.
Eloquent, thorough and powerful.