A religion that you were brought up with is a good moral code platform. Sometimes it is easier to teach someone who already has a moral background that you do not agree with than to teach someone who thinks they have no morals at all.
If James was raised a Catholic he should believe that he is born with natural sin. James believes that killing is wrong.
Now take Samantha who was not raised with any of the major religions. She does not believe in God. She believes that killing is wrong but did not have a logical argument why. Maybe her family never went to church, but they discussed politics and said that lets say fighting a war, and war was wrong and bad. Maybe they have family in an army and do believe that killing is necessary.
If we are going to try to bring someone around to our way of thinking, either James or Samantha, who do you think might sooner come over. Maybe James as he has a moral framework that we understand. Does Samantha have a moral framework? Yes. Do we understand it? No. Not without getting to know them. Speaking to them. Maybe Samantha already believes exactly what we believe in that there is no good or bad and nothing is determined but since we do not know the future therefore we have our subjective understand in an objective universe.