The case is being appealed, but the initial ruling holds that the host of a site can be held liable for the statements made by the posters.
As far as Mann goes, when one considers the implications of the fable, the hockey stick, and the damage done to science and scientific discourse and inquiry, not to mention the economic devastation wrought in the name of stopping a natural process attributed to humans (but in hiatus), merely destroying one child's innocence and damaging them for life (not a crime I view lightly) pales in comparison to what has been done to billions of people.
Interesting. So if someone on DU were to make libelous claims, DU could be held for libel?
But, wait! DU is liberal site. No (liberal/Dem) judge would allow that to go forward (using the current Dem favorite, "No standing").