You have to remember that most journalism is done on the fly. 

Language Log has a post today on selective (and distorted) quotation in news stories. Here is some speculation from the post:

"The journalist knows what (s)he wants to write, and what sort of facts and quotes are needed in support, and therefore manipulates the person interviewed so as produce suitable copy — in this case mainly by selecting a few suitable fragments from a long interview."

There is something to this. Reporters generally begin work on an article with expectations of what they will find. Sometimes they have been assigned the story by an editor who has a firm idea of what the story will be--and pity the reporter who comes back saying that there is no story there, or that it is a different story from what the editor envisioned. 

The quotations will, of course, support the thrust of the story, and they will be selected. Virtually all quotations in news stories that are not transcripts are selective.

To this we have to add consideration of expertise. Some reporters cover a topic long enough to specialize in it, much as, for example, Lyle Denniston developed extensive access and expertise during the years he covered the Supreme Court for The Sun. Such reporters still exist, but they are rarer. You as a source for a story are likelier to encounter a reporter who can charitably be described as a generalist.

You recall I said this is done on the fly. The reporter has to get a story today on the research in your study, and it is unlikely that he or she will have the time or expertise to consult other studies to evaluate the import of yours.

Thus Andrew Wakefield's study linking vaccines to autism gets widespread play. And when Jenny McCarthy types discover that they can prolong their fading careers at the cost of allowing small children to get sick, we have celebrities to write about. In America, when a celebrity, no matter how minor, climbs about a bandwagon, no matter how crackpot, widespread and prolonged news coverage is guaranteed.

Good luck with getting the same attention when you write that Wakefield's research and McCarthy's assertions have been entirely discredited. 

There are supposed to be corrective measures in place. Editors are supposed to be skeptical rather than credulous. Copy editors are supposed to raise awkward questions before publication. Hell, reporters are supposed to be skeptical. But the beast has to be fed, and we no longer believe much in editing, which costs money, so we process instead of edit.

Online media may have pressed the accelerator on this phenomenon, but if you look at the history of journalism broadly, it has pretty much always been thus. 

If I can say this without being acccused of special pleading for the trade, I wonder why you would expect otherwise. The shallowness of much journalism holds up a mirror to the cultural and intellectual shallowness that surrounds us.