In a sign of the times, small groups of dangerous radicalised idiots are an inevitable consequence of increasing polarisation. And once violence starts, radicalisation follows swiftly. A flow-chart showing the movements of these violent extremists would move from social division, towards polarisation and then to radicalisation. After radicalisation (which is actually not that uncommon) a very few will move towards the use of violence, And that is exactly what happened here. Interestingly, the media is referring to this pro-violent group (which included former police and military) as "ultra-right" in order to distinguish them from the (still legal) far-right.
This article from the New York Times points to the fact that most of the members of this group who were planning violence and murder against Muslim civilians and shops, belonged first to Marine Le Pen's Front Nationale and then gravitated to even more far-right groups (e.g.: Volunteers for France) before breaking away with the intention of adopting a strategy of violence and "fighting the Islamic peril." "All 10 defendants were charged late Wednesday with terrorist conspiracy, while some of them were also charged with illegal possession of firearms and the manufacturing of explosives."
Security services throughout Europe are increasingly concerned by the increased threat from "ultra-right" terrorist violence. We should never forget that, 9/11 aside, far-right or ultra-right terrorism, kills more in the US that Islamic terrorists. The impact of Anders Breivek's terrorist rampage must never be forgotten. Our best bet is that those who are attracted to this violent option are foolish amateurs and largely incompetent - and like the current bunch, caught by the security services before they can put their plans into practice. But if recent jihadist attacks in Europe have shown one thing it's that low-cost, low-tech attacks by amateurs can be just as devastating as anything professional terrorists are capable of.
Let's hope that the threat of ultra-right terrorism is hobbled by amateurism...