These skinny little fuckers now either feel like they *are* the mainstream, or they don't give a flying fuck about the rest of society
The way I see it, they're not far from the mainstream, and that's the problem. The distance between these white nationalists and the majority of people I know in real life outside of my own social circle is just a shade of self-image.
We still live in a country where nearly half the population votes in support of bigoted laws. Where a police officer can get rich off of donations for controversially shooting a black man. Where half the cultural discourse over a police shooting of an unarmed black person will revolve around how violent and scary black people are, and whether the victim in their history has proven themselves to be enough of a good type of black person. Where the drug war and incarceration trends are still horribly, horribly racist in nature and ravage majority black communities or are actively geared towards minority vote suppression. Where LGBT having basic human rights is still controversial, and many still hide who they are in public out of fear for their safety.
The only thing between all that and the violent bigotry of USA pre-60's is taboo. A cultural taboo has been established for decades where it was universally understood that you couldn't openly declare specific groups of people as inherently sub-human, or espouse direct violence or enslavement against them based on who they are. This not only effects how people behave in public, it effects how self-image interacts with thinking. Few would dare to self-describe as being an actual nazi or KKK member, because they've been raised in a society which strongly associates that with being a terrible person. Nobody, even actually terrible people, want to
feel like a terrible person.
What's happening right now is that taboo is being challenged. If our cultural narrative fails to adequately reinforce the idea that this taboo is still a thing, and the people challenging it are actually terrible people whose ideas are strongly rejected by society, then it's all out the window. That socio-psychological barrier between attempts-to-be subtle bigotry and To Kill a Mockingbird/chemically castrate the gays bigotry is no longer in play, and shit gets real.