When do people become white supremacists?

From the Mother Jones article Inside the radical, uncomfortable movement to reform white supremacists:

Starting in the late 1980s, Tore Bjørgo, a Norwegian sociologist, interviewed white supre­macists as they attempted to leave the Scandina­vian neo-Nazi movement. His findings were counterintuitive: Many became hardcore racists only after they had joined white supremacist groups. Rather than preexisting anti-Semitism or xenophobia, a cocktail of experiences such as isolation, depression, anxiety, or childhood abuse typically served as the stepping stones to extremism. This suggested that the behavioral and social rewards of participating in hate groups are perhaps more fundamental to understanding—and stopping—extremist behavior than the ideology behind it.

There's a certain psychological profile that seems common to those who join extremist groups of whatever sort. I worry that a lot of activity billed as "anti-racist" may be more likely to drive people into white-supremacist organisations rather than away from them.

Here's a different example from Deeyah Khan in the Vox article This filmmaker spent months interviewing neo-Nazis and jihadists. Here’s what she learned.:

... Part of the reason people subscribe to these movements is that they feel shunned in their lives, in their personal lives or in wider society. These movements are deeply rooted in a sense of victimhood, real or imagined. So if we exclude them, if we shout at them, if we condemn them, that completely feeds into that. And then the monster gets bigger, not smaller.

The point about victimhood potentially being real or imagined is important to recognize, and I think that it's a lot easier to sell people on the notion that they're victims rather than victimizers. On people's motivations:

... Much of it doesn’t come from hate. It comes from a lot of other basic human needs that are not being met. To be sure, there are political and social and economic factors involved on both sides, but if you dig deep, you find that it’s about much more than that.

I tried to understand the core psychological draw of these movements. I found that a sense of belonging or purpose was a major factor. These people join these groups and suddenly they have a sense of meaning in life, a belief that they matter, that their voice matters. It’s as though they were once invisible and now they’re seen.

Khan there also talks about the commonalities and interdependence between jihadists and white supremacists which I certainly agree with, but that's a story for another day.