Read here, here, and here. The vast majority of catastrophic global warming skeptic blogs, including 'C3', are not funded, nor supported, by some nefarious group that is "the best-funded, best-organized smear campaign" only known to the infamous, legend-in-his-own-mind, widely discredited, hockey-stick clown.
Unfortunately, the Mother Jones' reporter obviously chose to repeat Mann's own smear campaign against his critics and skeptics without the least effort investigating the veracity and accuracy of his smear. Combine this major shortcoming with other major errors in her article and one can easily surmise she's been snookered into repeating non-factual claims.
"For example, the standard line about the NAS panel's review of paleoclimate is repeated. I find it hard to believe that anyone with any self respect can continue to pretend that the other paleo studies are not undermined by their use of bristlecones (plus Yamal et al). This is such a simple issue that it does rather shred a journalist's credibility if they feign ignorance of it. The author Kate Sheppard blagged a copy of HSI from the publisher, so she knows it's a problem. I wonder why she didn't mention it?"