Imagine the Earth in which the vast majority of people seriously believe in Santa, or some slight variation of him, and live their lives accordingly.
In this society a person cannot be elected as the leader of a country unless he believes in Santa.
This society has fought wars over which variation of Santa is the 'correct' one.
What would you think of this world? Of these people?
If you have imagined what it would be like to literally live in such a society, then you have just seen the world through the eyes of an Atheist.