I think it all stems from a lack of understanding of subtlety in arguments. For example, when you watch mainstream news, all you see are the extreme points of an issue. You never really see the middle ground, and you never really see any rational arguments. You see either fire and brimstone, or puppies and sunshine.
Take climate change for instance. The only arguments that come up are that either (a) it's not happening, so go fuck yourself; or (b) WE'RE ALL GOING TO CATCH ON FIRE THEN DROWN AND IT'S THE APOCALYPSE. It's never; the world is headed in a direction that we may have control over, but even if we don't, we should probably try to do a better job than we've been doing.
I don't know when it started, but it seems that anytime an even remotely controversial issue comes up, we never see a rational explanation, it's always hyperbole and ridiculous nonsense. It's like people believe that every other human is mentally incompetent, and need to be shown the most extreme example that could possibly exist for an argument to be effective.
For good examples see global warming, immigration, and my recent favorite source of 'the sky is falling' hyperbole - CISPA.
Please note, I am neither endorsing, attacking, nor am I any other verb-ing the items I listed. I am simply saying that a majority of the arguments about those items come across as ham-fisted and ridiculous.