If you take the most emotionally unstable 1% of the most politically marginalized 1% of society you have a collection of people who have the potential to do unthinkable acts for beliefs which are alien to most people in mainstream society. It sounds like a tiny collection of people, but in North America there are (roughly) 30,000 people who would fit into this grouping and they exist (in proportionate numbers) for all political ideologies we have identified (and some we really haven't).
The primary difference between "Right Wing" extremists and others who commit acts like these is how the media (and others) respond to it. When a person holds an ideology which could potentially be labeled as "Right Wing" the label is attached to the individual and the act and it is repeated over and over again, when the act is performed by another group the media generally portrays the incident as the act of an unbalanced individual.
