How are we to reconcile the fact that white supremacists are increasingly ethnically diverse?

This oxymoronic conundrum has recently been confusing Cristina Beltrán. Obviously, Donald Trump is racist, and supporting him is a racist thing to do, and the protest-riot-insurrection-domestic terrorism that occurred last week was totally racist. And yet, as she wrote in the Washington Post:

The Trump administration’s anti-immigration, anti-civil rights stance has made it easy to classify the president’s loyalists as a homogenous mob of white nationalists.