I read the Climate Progress blog regularly. Actually I skim it. This entry is typical on Joe Nocera's piece on Keystone XL.
"So far, it seems as if Nocera’s views on global warming derive from reading the likes of the widely debunked physicist Freeman Dyson and attending Exxon-Mobil shareholder meetings, which causes him to dismissing knowledgeable people who express science-based views"
There seems to be a notion, on the left and the right, that the best way to argue a position is to call those who are unconvinced or oppose to you, stupid, ignorant, venial and corrupt. For the climate crowd the label "denier," is shorthand for that characterization.
But you can admit the climate is changing and not agree to the Al Gore/Jim Hansen/Joe Romm solution. Or you can agree the climate is changing, but the predictions of the feedback loops are highly speculative.
Calling me a "denier" denies you the chance of persuading me.