It’s more than just being against Jesus’s “people” (both brown skinned and Jewish, things white supremacists hate), they also hate the teachings of Jesus, which would be considered socialist in nature these days, or “woke” even.
Cutting through all of their bullshit, these fascists just want to control the in-groups, and in America Christianity is one of the major in-group. Similar stuff is happening in India, where the Hindu nationalists have power and are growing more and more aggressive towards their Muslim country men and other minority groups. Once the major in-groups are under their control then the really fascist stuff starts happening, like forcing people into ghettos and concentration camps under the threat of violence, with secretive ultra-violence.