Protection or sadism?
What are the motivations of the parents in Dogtooth?
The father insinuated to Christina that she was a bad influence on the children. Is the bad influence of the outside world all that he is worried about?
At times, it seemed as though the parents enjoyed figuring out the fake details of their children's reality--when the wife tells the husband that she is pregnant, for example, or when they decide that the brother on the other side of the wall must "die."
When the father beat his daughter with the VHS and Christina with a VCR, was he enjoying the control, enjoying the violence, punishing a rule-breaker, freaking out that his daughter should learn anything that he had not taught her? Something else?