"But think of the children!"

Yes, NZPols has resorted to this tiresome old line...

Recall that this is in the context of preventing violence against children, something which is usually considered to be a pretty serious rights violation itself.

Yes, it is. But that doesn't mean that you need to intrude into the core of everyone's lives in order to protect them.

Normally, we "protect" people from violence by punishing those who hurt them. In the case of children, we also have mechamisms to remove them to state or foster care if their present guardians are inadequete. While the latter does intrude into that core protected area (people's children are usually pretty important to them), you'll note that it is done on a case-by-case basis on (ideally strong) evidence. We do not squick everyone simply because some are bad parents.