Great topic and post! In my opinion, if the children are harmed or malnourished, that should be cause for investigation. Also if they are being taught to actively harm others or cause undue offense.

Otherwise, I think we might tread into thought crime area, if we try to dictate what others can think. Even in the case of something like the Nazi example as long as the children are taught to follow laws. I don't see how people can be forced not to think or say their beliefs.