A recent exchange between Benny 'Hill' Peiser and Robin McKie in the Observer shows why; Benny used an invented quote by Sir John Houghton to make his point - quotes, like any form of evidence need to be reliable. A sceptic would approach all sources of information with a sceptical mindset and demand authentication. What Benny did is took a talking point from the denialosphere and simply recycled it for use without confirming it's truth. That is not a sceptical mindset - it is the mindset of a propagandist. Propagandists exists to make a point whatever the data. People who have made their mind up about the conclusion before considering the data can never be sceptics. The denialists point to the errors in the IPCC as proof of their claims - yet they were making the claims event before the errors were uncovered. The are still making claims about conspiracies and lizard-men new-world-order shit now;
In the heat of the debate, the representative Mike Noel said environmentalists were part of a vast conspiracy to destroy the American way of life and control world population through forced sterilisation and abortion.
Put simply the IPCC and the scientists behind it are accountable and are part of a process - errors made (and I am surprised there are not more) are both inevitable and part of the science. They are expected as part of the process of learning and understanding a complex system. By contrast the denialosphere is able to make the craziest and wildest claims; make shit up, cherry-pick results and lie, lie and lie - without any accountability. Now I am sure there are the odd one or two genuine sceptics in the ranks of the denialosphere, but they are undoubtedly a tiny, tiny minority. If the denialist movement was stuffed with scepticism they'd be asking for evidence of such nutty shit-loon claims and holding the authors of them to account. They don't because they are not sceptics, but denialists.
...and it the cap fits...