Modern white nationalist groups grew out of the fight against civil rights. The Council of Conservative Citizens formed in 1985 out of the White Citizens' Councils that fought school integration in the South. In the 1990s, publications like American Renaissance argued for white racial identity in academic language. Around 2010, leaders like Richard Spencer rebranded the movement as the "alt-right."
The Unite the Right rally in Charlottesville in August 2017 brought these groups together in public. A white supremacist drove his car into counterprotesters there and killed Heather Heyer. In March 2019, after the Christchurch shooting, Facebook banned praise of white nationalism and white separatism and said they could not be separated from white supremacy.
White nationalists often say they only want to protect their own group. But the goal of a nation defined by whiteness depends on shutting out, removing or controlling people of color. That's why ARD and most researchers treat it as part of white supremacy.