Lynn, I would actually argue that your post over-simplifies and generalizes points that may or may not be applicable to different children and families. You say that 6-8 year olds are fearful because of their lack of understanding how to put things into perspective. This has not been my experience *at all*, so obviously it varies from child to child and family to family. My dd has never been fearful. Listening to NPR has spawned tons of REASONABLE discussion and real-life examples that we can talk through. Hearing these stories allows ME to put these life lessons into perspective based on what I know will be the best way to approach it for MY child. I don't want dd to learn about these things from a 3rd party. I want to be the one having these discussions with her. By listening to NPR, I've always been the one to talk *first* with her about the real world, and for that reason, she seeks me out to talk about things she now hears at school. I have an only, who is 9, so I'm not sure if she is the norm or not, but these stories have never made her fearful. They have made her sad. They have even made her more empathetic toward certain causes. They have not desensitized her, but they have given her real-world knowledge.
For example, we live very close to an international airport. On cloudy days, the planes sound like they are going to land right on top of our house. From an early age, dd knew about 9/11 and has even seen the pictures (including of people jumping). She knows what happened, yet the planes over our house have never even bothered her. She has had the reasoning for years that this was an isolated incident and that what happened there is not a tangible threat where WE live. In fact, isolating her from it would only have proved to be damaging because her world includes Islam and the last thing I want her to be exposed to is the opinions of others about it (which may or may not include serious religious bias).
So, I personally disagree that ALL young kids shouldn't be told about a reasonable amount of what is the very real world we live in. You have to determine that for your own child. If you have a child that do not have the cognitive ability or emotional maturity to reason these things through then of course you do what is best for them. I would argue that not talking about these things give others the chance to do so first, though. From whom do you want them to hear about these things? For us, I wanted it to be one of the parents and not friends or teachers or neighbors. Our philosophy is that if dd can comprehend the issue at hand, she is old enough to explore it. This hasn't failed us yet, but of course what works for our kid may not for others. A generalized statement doesn't apply to her and I'm sure it doesn't to many other kids.
ETA: And honestly, I've never heard a single "sensationalized" (ala Fox News or Rush Limbaugh) story on NPR. They are a tame news source compared to what is available out there and seem to be as factual and fair as possible. As an early introduction to news, I think NPR is awesome.