You know, I used to feel the same way. I have a cousin who lives like that. She home schools her kids, they are very, very religious, the kids have no contact with anyone not like them. Then, a couple of months ago, I went for a visit.
This is a family that is loving, compassionate, not nearly as judgemental about others as I thought they'd be, and extremely happy. They read about others who are not like them and stay informed about current affairs. They are aware of the "world out there", just choose not to join in many of the activities of that world.
After seeing some of the things my daughter was exposed to in her teens and some of the pressures so many kids are experiencing today, maybe families like them aren't so wrong. It's not for me but if it works for them...