The main reason is they can't comprehend a little basic science and statistics:
Slice your average environment correspondent through the middle and you're going to find a left-leaning liberal arts graduate who is utterly out of his/her depth. Their world view is being swept from underneath them and they are being shown—in ways that they do not really and have never had to understand—that the guys they thought were the goodies are in fact "at it" and that those they have spent a decade disparaging as deniers were in fact spot on.
Another thing is that these climate "scientists" (Jones, Mann, Hansen, etc) have staked their careers on global warming. If and when it is revealed to be a fraud, their careers will be over. Therefore they have nothing to lose by lying, screaming, and bullshitting until the game is over.