I think scientists are partly responsible for their loss of credibility by bowing to leftist pressure and endorsing slogans like "global warming", "global cooling", "the population bomb" and other such nonsense.
Similarly, pick up any recent scientific publication on climatology. Now, notice that there are no slogans. Instead, there are peer reviewed studies which present hypothesis, experiments, and conclusions. True science is not "political," and if you believe it is then you are simply the byproduct of the media. Scientists themselves say that the media doesn't cover science well -- so perhaps you shouldn't judge scientific opinions based on it?
There have been many scientists to have admitted that they have kept their mouth shut when they oppose the status quo for fear of losing jobs or failing to gain funding. The concept of "a few bad apples" is certainly not new.
When 1 whack job PDH with 3 assistants and a new theory is given just as much air time if not more as what 100,000 PHD's think on the average story people can't tell what the trends really are. It's a breaking story when Bubba and his 6 month study of 50 people says soda might cause or prevent cancer, but it is old news by the time the results of a 10 year 50,000 people study disprove that link.