An article published on CNN’s website makes an unproven claim that pressure cooker bombs like the ones used at the Boston Marathon terror attack are a “signature” of “right-wing extremists.”
The article says (emphasis added) :
A senior U.S. counterterrorism investigator told CNN that pressure cooker bombs have also been a signature of extreme right-wing individuals in the United States who he said tend to revel in building homemade bombs.
This specific claim that “pressure cooker bombs have also been a signature of extreme right-wing individuals in the United States” appears to be completely unsubstantiated. Not a single example is given even in the CNN story itself of anyone other than al-Quadea using a pressure cooker bomb.