NBC already did what they needed to do. They outright fired the producer who edited the 911 tapes: http://www.foxnews.com/us/2012/04/07/nbc-news-reportedly-fir... As they should have. NBC also issued the obvious reiterations and reported on them. CNN has issued retractions as well. But all of that is the bare minimum that needed to be done in response to despicable reporting in the fist place, and frankly, THAT is the problem that is not going to go away. Our for-profit media outlets are defined by the need to sensationalize to grab eyeballs. It's all about the bottom line. Fast and loose Newzertainment that covers anything that will make you sit up at attention in 2 minute intervals. I don't think there is any accountability in the mainstream media which is why I don't watch it. I will reference it though. I get my news from a plethora of sources online. The major news outlets are just a few data points of many in this mix.
Your understanding of an issue will always be a function of how much effort you expend studying it.