Blogs, Limbaugh, etc.
There are well-funded right-wing folks whose only job is to smear the messengers. The info gets fed to blogs and folks like Limbaugh. And then something as serious as man-driven climate change is trivialized by statements such as,
"Look at those polar bears! Picture taken in 2004, and they were fat, dumb, happy and safe. It's all lies. Global warming is a pile of crap!"
And other people who read those blogs take the information and disseminate it. It works well for them.
Less publicized but the same tactic as Clinton used in his "bimbo alerts", wherein he immediately smeared any woman making an accusation.
Arf