(I'm not sure it would be that small a minority, those who care a lot about abstract principles - nerds like us, religious fanatics, political activists - are a minority)

This is a great point. I'm pretty sure that if people thought about it rationality most would prefer Brave New World to what we have. I don't think I would, precisely because I'm part of the weird group that is pretty attached to some abstract principles. However please note that on average person in the Middle Ages took religion very seriously.