Do you need to be a climate scientist to make the argument that Big Oil has something to lose by carbon emission reductions?
Beyond that, this is a typical ad hominem fallacy. Related to that is the argument from authority.
http://www.skepdic.com/adhominem.html
This site lists a number of climate change scientists with impressive credentials, as contributors. Still, we have to more interested in what is being said, not who is saying it. We should give more weight to what an "expert" is saying, but not assume that the argument is correct.
Both sides are guilty of this.
http://www.realclimate.org/index.php.../contributors/