Quick thing to add here. Main masonry indeed does not allow Atheist members. However, there are various divisions of Masonry that do.
Most recognized among them is the Grand Lodge of France.
Grand Orient de France - Wikipedia, the free encyclopedia
However, many members of mainstream FreeMasonry feel that allowing Athiests goes against the principles of Masonry, since it originally did, and still does, encourage people to follow and grow in their religion.