These supremacist groups are analogous to cults.  Preying on the disenfranchised and unconnected.  People with difficult personal issues, no sense of belonging and who are loners.  Many likely do not have jobs.  

One fear I have is that with income inequality growing due to the current economic environment and due to unstoppable automation, the number of potential young people who fall prey to these horrible white supremacist groups (Neo-Nazis, etc.) will grow.  I think we, the USA, needs to start preparing and thinking about closing the inequality gap to decrease the potential for young people to feel disenfranchised.  In the long run, it will help everyone.  Providing alternatives to the disenfranchised will shrink the potential pool to recruit from until someday they will be a fringe of the fringe.  A spec of idiocy in a universe of good.