I saw an article on Salon.com or perhaps AlterNet, and reading the comments I was moved to comment myself; I assembled the following out of material I already had on my blog, but in the comments I got several compliments on it, so perhaps this is a happy combination of elements. -JBH
Religion has its benefits and harms. One of the major harms that it does is to teach a false theory of ethics.
Religious folk misunderstand morality at its roots. Religion teaches a child's view of ethics, that "being good" means "obeying your parent". Just as religious faith is believing what you are told, so religious morality is doing what you are told. Religious morality consists of obeying the alleged will of God, an invisible "Cosmic Parent", as reported by your chosen authority. But obedience is not morality, and morality is not obedience. We can all think of famous people who did good things while rebelling against authority, and others who did evil things while obeying authority.
Religious folk may be Good Samaritans or suicide bombers, it depends entirely on what their chosen authority orders them to do. If a believer, or a community of same, wishes to make war or keep slaves or oppress women, all they have to do is persuade themselves that their god approves. This seems not to be hard, and no god has ever popped up to tell believers that they were wrong. They do not have a code of morality except by the convenience of the priesthood. What they have is a code of obedience, which is not the same thing.
Adult morality is a means of maintaining peaceful and cooperative relations with your neighbors. If you want peaceful relations, don't kill, steal, lie, or break agreements. As Shakespeare wrote: "It needs no ghost, Milord, come from the grave, to tell us this."
Living beings evolved by natural selection are going to value the health of their families, "inclusive fitness", where "health" is the ABILITY to survive, and "family" is "all who share your genes, to the degree that they share your genes." Their desires are shaped by natural selection, and inclusive fitness is what natural selection selects for.
Social animals, who survive by cooperating in groups, have a "natural" standard of ethics: The Good is that which leads to health, The Right is that which leads to peace. A "good person" is a desirable neighbor, from the point of view of people who seek to live in peace and raise families.