"The results indicate that patterns of far-right radicalization in the United States are consistent with a complex contagion process, in which reinforcement is required for transmission. Both social media usage and group membership enhance the spread of extremist ideology, suggesting that online and physical organizing remain primary recruitment tools of the far-right movement."
Interesting read. That said, the admittedly narrow focus on the PIRUS database ignores what is clearly a more immediate problem: those who may not act, but support the action.
When a group calling themselves a militia plan and rehearse the kidnapping of a governor and the potential use of lethal force against law enforcement, they are not conspiring in a vacuum. Material support and psychological encouragement coalesce with fervent political justification (from talk shows to the White House) to give credence to such action.
In this regard, there is little difference between the radicalized domestic terrorist in this or just about any other country. The so-called extremists and lone wolves have their pack of backers, whether they be located locally or virtually, and it is they who should be the object of our deepest concern.