What does it mean to be an atheist?
It means any righteousness ("Moral Values") comes from self. Which would make one self -righteous
I believe this is a common misunderstanding of atheism. Atheism means any righteousness doesn't come from a creator or any group representing this creator (for example by claiming their writings are inspired by God).
This however doesn't necessarily imply that righteousness comes from self.
Righteousness always originates from a community, never from an individual!
Problems arise when you believe your community is directed by higher forces and therefore possesses a higher truth.