Are atheists more moral than theists?

Yes, they are.
Atheism destroys excuses for people to subjugate others. It frees people from religious biases and imperatives and allows them to see the human equation.
Once you stop thinking of others as less important (because your religion tells you you're one of the chosen people), all others  must be seen as fellow human beings.
Atheism's complete lack of the religious 'chosen people' idea necessitates basic human compassion and equality.
When we are all equal as people, we tend to discuss more and demand less. A lack of religious arrogance would mean an end to many of the worst human woes.
Atheists are often asked, "How can you have morals without God's laws?"
Atheists are more moral than religious people because we choose to be moral, instead of being moral because we're afraid of going to hell.
Morality can't be forced. It isnt morality if you act in a moral fashion because of the threat of torture.
Morality is not based in fear.

The things that make religions immoral are simply not present in the atheist non belief.
• Atheists do not believe they are a chosen people.
• Atheists do not have an easy method of forgiveness for immorality.
• Atheists do not cover up for each other's immoral acts. In fact, much like scientists will denounce a bad hypothesis by other scientists, we argue the immorality of atheists as strongly as we argue religious immorality.
• Atheists do not have a belief we have to put before evidence, so we're more honest to ourselves.
• Atheists do not have a book telling us to convert the world to atheism.
• Atheists freely choose to live moral lives.
• Atheists don't even like to capitalize 'atheist' because we don't want to let even the name become dogma.
• Atheists do not kill for atheism.

Atheists are good and moral people, who just happen to not believe in gods.