I was reading through this piece about the discussion of race in traditional and online media on Nate Silver's FiveThirtyEight.com this morning (great blog, by the way) when I encountered the term "nutpicking." According to the link Silver provided, the term was coined "to describe the increasingly common practice on the right (and yes, on the left, too) of cherry-picking random comments or hate emails to smear your entire opposition as raving nuts." (I also like the description provided by one of the commenters: "I like to think of it as 'picking peanuts out of poo.'")
It looks like the credit goes to Kevin Drum for first identifying the practice in the wild and then promoting the name. Great term to describe an increasingly common phenomenon. I am certainly going to incorporate it into my vocabulary.