Great job evaluating opposing arguments as objectively as possible. (Though I suppose maybe that is your maximum level of objectivity... Which would be sad.)
This is precisely why anyone should read any source of "information" with objectivity/skepticism. Because the "scientists" that publish it have all the same human biases that I and the quoted poster have, and much like him, they may not be able to restrain them.
I am as objective and skeptic as the next person - I have no idea whether GW is man-made or natural. I do however, realise that the continued misues of natural resources is ultimately not going to help anyone.