Crying wolf is always a bad idea. Deception is harmful and so is the loss of credibility. It is awful when it is done in the supposed service of a greater good.
Lately, this has been the last refuge of green scoundrels. When the whistle is blown on some over-the-top claim about the environment, the response has often been that there is something virtuous about lying for a "good cause."
Tell that to Stanford Prof. G. Pascal Zachary ("The silver lining of impending doom", in today's NY Times) who even links the tactic to Joseph Schumpeter's idea of creative destruction.