A science journalist has usually studied some natural science but has to cover all of them and has to simplify a lot, so a trained expert will find a lot of inaccuracies. This is not true for the journalist who reports international events and affairs - these are based on much simpler facts such as "which government decided what" and "which spokesperson of some organisation said what when". It's much easier to get worldly facts like this right, which mostly come from multiple news agencies anyway, than describing news about theoretical physics to laymen in terms that are 100% accurate to a physicist.
In a nutshell, I'm not so sure that the effect really exists in any significant way.
Another issue is, of course, from where else you would get accurate news if not from journalists and press agencies. I've never heard of any reasonable and viable alternative from critics of traditional news media. Cell phone videos by citizen reporters with hysterical voice over can hardly count as a good substitute. Neither are copy&paste news aggregators or bloggers.
At some point you've got to trust your newspaper (or read a better one!) unless there is explicit counter-evidence from elsewhere against the story. Most botched reports get corrected very fast anyway.