Because skepticism should be the natural state of being of any intelligent person.

Unwavering belief and fanaticism is inherently dangerous and stupid, yet unwavering belief and fanaticism is all global warming has had for the past decade. The fanaticism has clearly got to the point of doctoring evidence and attempting to sabotage critics. How long would it have been until we got to an asinine crusade against non-global warming believers . . . oh wait, that's already started amongst the GW scientists!