The fellow in the photo holding the threatening sign is symptomatic of an increasingly paranoid quality to American life. (By the way, sir, you have "your" where you should have "you're.") A dangerous trend started at least as far back as Sarah Palin's irresponsible campaign rallies in 2008, when she allowed the flames of hatred to be fanned. The Secret Service reported a spike in the number of death threats issued against Barack Obama.
Now, as President Obama, the Secret Service reports a skyrocketing of death threats, compared with the number received by President Bush. As with any president, the large majority of such threats are hoaxes, but the sheer volume and the sheer venom can't be dismissed.
With town hall meetings turned into town "hell" meetings, with people screaming and refusing to allow others to calmly state their opinions, I do fear that something horrible will happen. One thing we should not be able to claim is that we had no way of seeing it coming.