Why do Atheists and Agnostics feel they are smarter and intellectually superior?

That is a bad understanding of faith. That doesn't sound like one who is smart. And being smart will also involve intellectual honesty, not caricaturing anybody else's belief. But I think atheist and agnostic think so often that they are smart because those who believe are many a times unable to give reasons why they believe. However, it will backfire when those who do not believe also fail to give reasons why they don't believe. To say that they don't believe because they don't see will not be a smart answer.

Reason requires logic and logic requires proof. If a person postulates the existence of something then the burden of proof is on them. A person that says that there is no god has nothing to prove while a person who says there is one should be able to prove it. I don't think this will backfire on me.

If you will believe in only those things which can be proved you cannot prove that the man you call your father is really your father. If you meant that you want to be proved with 100% certainty. Reason and logic can take you only to some extent. I think when one says that God exists and another says that God does not exist, both need to show the reasonable nature of their points. Because both the individuals are making statements as if they know what they say is true. Both when one says 'I don't know' then the burden of proof lies not upon her.

Nice answer, it is the same old problem : People think that all atheists are the same. We aren't! There are atheists that do consider themselves intelectually, morally or both, superior to others, many don't. Many just want to live their lives without having religion imposed over them.