You should pre-judge most things. Most Birds? Fly. Met a penguin? Unlikely but cool, now you adjust for that case. South Africans? Kill Boers. The ones they meet and get to know, are the only ones they let past the electric fences.  Unless you want a microwaved baby, starting from prejudice and not trusting every stranger (Stranger=Danger. Seen some signs a stranger isn't dangerous? Good, put slightly more trust in that one than others.) is a good idea. People outside=You don't want inside, at least until you know more. Or do you not lock your doors?