Just as the existence or non-existence of a God (or gods) is not dependent upon whether or not they are believed in, the existence or non-existence of atheists is not dependent upon your belief or non-belief in them.
There are innumerable ideas concerning the nature of reality. One school of thought is that the existence of anything DOES depend on whether or not they are believed in. Who knows, maybe even the vast right wing conspiracy actually exists in Hillary’s world.