If you interpret “cult” slightly less literally, I’m sure you can think of some fairly vivid examples of cults that have seized control of the governments of even developed countries, and used that power to indoctrinate children via the official school system. In a situation like that, some homeschooling might have even been beneficial, compared to the alternative.
I would not make it so easy for the fascists to excuse them as cults. Fascists all know what they want (exterminating everybody not deemed worthy for their race), and they all owed their success to "conservatives" who would rather support them in their mission than to give up privileges.
Possibly Islam with the shit that goes on in Saudi-Arabia and other Middle Eastern countries, but heh these countries are majority Muslim anyway so homeschooling would not fix the issue either.