As far as I know, foxes don't eat human children, it seems to be an urban legend. They certainly do eat fox children for whatever reasons.
Humans can't legally kill human children, ancient Sparta and modern killing of child soldiers being obvious exceptions. Foxes, however, most likely don't have any laws.
Some time ago, I've read in some work of fiction about a fox eating it's children and then falling to sleep. It impressed me greatly. For some reason, lately, I often remember this event.
It's one of the cultural differences that leave a permanent mark on an observer's memory. The equivalent (although still less weird) would be for humans to be able to adopt sons and daughters for any reason at any age. Since some human families are really fucked, there is no logical reason for humans not to have massive amounts of adoption and of people changing their families. I think foxes understand this and this is why they choose to do the things they do.
I think the most important thing to find out when trying to learn the difference between two groups is what one group finds weird about the other, that the other doesn't think is weird. Humans also consider foxes to be clever, but they don't think that being clever is weird, which means it's not most important.