It's obvious NBC News is airing Cho Seung-Hui's videos for publicity. Does anyone really need to know what was in his mind, given the established fact that he had a history of mental illness? Cho Seung-Hui is responsible for the largest mass shooting committed by a single person in American history. That's enough. He shouldn't need to make any more of a mark.
NBC's news pieces did what they were meant to do. Ratings went up and NBC Nightly News received some publicity from competing news organizations (who at least could have not identified NBC News by name). It's hard to see how any news organization in NBC News' position would act differently. Even CBC News' decision not to air any part of Seung-Hui's ramblings can be interpreted as a business decision, moral underpinnings notwithstanding. News is a business, like anything that can potentially make money. What the brouhaha with regard to NBC News really illuminates is that the media can take the bait and then feel sorry for themselves for doing so, and that they do it often. It's a duality that should never exist in the first place.