I think you figured it out. It’s not about immigrants, it’s about undesirables.
And those can be political or social - look up the first targets of German or USSR occupation in 1939 Poland, or who Khmer Rouge killed.
The goal is to keep the docile, undeducated masses, and everyone that “stirs the pot” gets erased.
I lived in a similiar belief about my country politics, and now I know there’s no easier thing than to indoctrinate children.