See Slate's complete coverage of the Gabrielle Giffords shooting and arrest of Jared Lee Loughner.
If you want the harder stuff, that's easy to get, too. Timothy McVeigh had to hunt for his copy of the Turner Diaries. In five minutes on his parents' computer, a paranoid person could obtain that book; the "Protocols of the Elders of Zion"; any number of fire-has-never-melted steel documentaries about 9/11; and David Icke's theories about the shapeshifting Lizards who control the world.
Loughner's particular brand of paranoia was incoherent. "I know who's listening: Government Officials, and the People," Loughner wrote in one of his YouTube essays. "Nearly all the people, who don't know this accurate information of a new currency, aren't aware of mind control and brainwash methods. If I have my civil rights, then this message wouldn't have happen[ed]." But he was using his civil rights to publish a video essay; if government officials heard him, it's because they clicked on it.
On Saturday, before we knew much about Loughner, an Arizona Tea Party activist told me the incident had made him think about how he talked. "Should I talk differently when I describe the Founders and compare what we're facing to what they faced?" Patrick Beck asked. "Could somebody imply that I'm calling for a revolution?"
I've thought about that as I read more about Loughner. Beck was thinking about how to calibrate what he said so that the craziest person in the room wouldn't take it the wrong way. This is undoubtedly what Rebecca Mansour wished she'd done when Democrats like Giffords started complaining about the map of targeted seats. And I suppose that's what Bob Brady wants to do, with the force of federal law and prison sentences. But what's the long game? If someone like Jared Loughner wants to develop bizarre ideas about government based on obscure online theories—or based on nothing at all—no amount of civil dialogue will prevent it.