Here’s what’s actually interesting about any of this: a Christian committing a crime is a person not living in conformity with their belief system, so is an atheist not committing a crime.
Christianity’s moral demands are the foundation of any criminal or civil law (don’t steal, lie, cheat, kill, harm). When a Christian commits a crime, it’s not as if he’s doing what his religion teaches him to do; he is doing the opposite and is not living in conformity with the teaching of his religion.
However, atheism is based on the foundational concept of the non-existence of objective truth and thus, the non-existence of any objective moral standard. Therefore, when an atheist lives a life in conformity with criminal and civil laws which themselves are rooted in objective moral standards, that atheist is living contrary to his “religion.”
So who cares why more Christians commit crime than atheist. The real question is, why does any atheist live a law abiding life?
Maybe it’s because they don’t really believe what they believe (nihilism).