But of course they can't speak to everyone...including the tribes etc...thus the scripture I quoted is what they use and they explain it by saying in the time of the end the preaching will increase until it is being preached in all the earth and then at some point, God will call time when it has been preached to his satisfaction because they will never cover the earth before Jesus comes at the Big A.
That's still effed up though. To think that people serve a god who will kill billions just because they never heard about him. After all, a person's choice of religion is mainly influenced by where they were born.