I suspect the recent shootings of Colorado's prisons and two prosecutors in Texas have prompted the CNN piece by Peter Bergen 'Growing threat of extreme right-wing violence':http://edition.cnn.com/2013/04/04/op...nce/index.html

At the start:
While American politicians and the U.S. public continue to focus on the threat from jihadist extremists, there seems to be too little awareness that this domestic form of political violence is a growing problem at home.

From 2002 to 2007, only nine right-wing extremists were indicted for their roles in politically motivated murders and other types of ideologically motivated violent assaults. But between 2008 and 2012, the number mushroomed to 53, according to data collected by the New America Foundation.
The NAF data:http://homegrown.newamerica.net/

CNN and NAF have some interesting facts / statistics and Peter draws attention to important facts:
Fifteen right-wing extremists were indicted in 2012 ...only six people who subscribed to al Qaeda's ideology were indicted on terrorism-related charges in the United States....it's striking that the jihadists charged with crimes were much less likely to have actually carried out a violent attack before they were arrested.