Let's look at the average TV sitcom. Without doubt, there is no talk of God or religion in these; and there is not even a vestige left of Christian sexual morality. There is no God-talk and chastity is not even considered as a value. However, I would argue that there are any number of principles that are taken for granted, albeit in non-Christian language, which reflect the basic message of Christianity. Most of these shows take it for granted that we must help our neighbor,  be honest, and do the right thing. Some episodes end with a message about maintaining our hope in the face of discouragement, on being trustful and working for a better future. There may be no talk of God, but the writers take it for granted that their audience share their trust in the future and on the need to be moral. 

Years ago in a university course, one of the students told the class that he didn't see any need for religion.  
“As long as we try to help our neighbor, what is the need for religion?” he asked. 

I said, “Where did you get the idea of helping your neighbor?”

“Well, that's obvious,” he responded. 

I then explained that this principle is not obvious and there have been many in the footsteps of Nietzsche who have argued that this idea of helping the weak is the sick error that Christianity brought into the world. This is only one example of the morality that so many shows and so many people, like my student, think is obvious. To me this suggests that Christianity has been more successful at changing the world than we have thought. 

Nietzsche assumed that, once belief in God had disappeared from the world —as it had in his time—, most of the morality based upon that belief would disappear as well. I think that is the thesis of his book, “Beyond Good and Evil.” To his amazement and disgust, people who claimed to be atheists continued to talk about and practice morality, a morality which only makes sense if one accepts the Christian God. 

Does that mean that, if the morality continues “in a society's bones,” we can do without the whole sub-structure of religion? Here is my thought: For at least one generation the basic directions and morality of a religion remain even if the sub-structure of faith disappears. But after two (or more?) generations, the upper structure falls through without the sub-structure. Suddenly, an individual or a society wakes up and says: “Why should I continue to follow these directions and morality any longer if I don’t believe in the religion?”

At that point, that society will NEED to be evangelized if it is to survive. The question is: How much time remains before we get to this point?