Call them separatists.
Either they agree and then they have to own it, and then you can demand they make good on their beliefs or they have to say they are not, which makes them willing collaborators with white racists, which destroys the arguments of racism.
Separatists won’t do. The “pilgrims” who came here to start this country didn’t call themselves pilgrims. That term came along in the 1800s. They called themselves Separatists and are my direct ancestors.