They always go after the notion that these things are the work of right wing extremeists. I am not suggesting that there are none who do this kind of thing; the left doesn't have the market cornered on whackos, but it does almost seem more like a left wing tactic so they can point the finger at the right. I think it's all stupid personally. My guess is that it's somebody who doesn't know the difference, just a loose cannon with his panties in a wad over some perceived injustice to himself and whether it is labeled right or left wing will ultimately depend on what issue that perceived injustice is regarding.
What was it .. 44 pipe bombs in 3 states .. whoever it was had planned this for a while