For many atheists, it is a long and lonely road we walk until we discover what religion is all about. And for those people, we have to use rational thinking and a critical examination of the facts.
Too many theists are raised and conditioned from birth that there is a god, no question, mike drop. I know, I lived in such an environment.
So they attempt to rationalize why a person became an atheist, and instead of listening to an explanation why atheists are what they are, come up with their own reasons because they fail to exercise their brains and rational thinking when it comes to religion.
One more important factor. I left religion for good reasons. Most atheists do. Too many theists do not understand that they should park their beliefs when it comes to examining important issues.
To them we are rejecting god, but the truth is we are rejecting lies and bullshit.