Scared Stiff

So, I just watched 20/20's Scared Stiff: Worry in America. Very interesting show. At the end, there was a segment about how there is actually a lot of good news about society today. The segment was interspersed with clips from news programs reporting bad news. These clips were then debunked as being untrue. It was explained that there is so much bad news in the media because it sells.
   But this just brings up the following question, "who can you trust?" John Stossel ostensibly debunks a number of worriesome issues  (e.g., dangers of vaccines). Why, however, should his media presentation be trusted any more than the media clips he debunked? In the segment about vaccines, for example, he seems to have stacked the deck in favor of the pro-vaccine scientific establishment. There are arguments against vaccines that seem to be deserving of a response (e.g., rates of infections disease began to decline dramatically well before the introduction of vaccines). Stossel did not present an articulate anti-vaccine argument. How can we evaluate John Stossel's claim that vaccines are safe without having heard the anti-vaccine position?
   John Stossel may well be right on target with every one of his segments. But my questions how do we evaluate competing truth claims?