I haven't dug through the entire thread, but it's a shame such a reasonable and rational question got bogged down so quickly in biblical moralism. So, I'm going to, instead, give my personal response to the initial query:
I believe nearly all of us are born with inherent empathetic impulses. I make exception for those who are legitimately defective in that department (a rarity, I assert). As someone has noted, studies have hinted that empathy/right and wrong are instinctual traits. Therefore, most of our ethical tendencies are the result of "nurture". Most of us grow up in generally ethical environments. Some are based upon religious tenets, and much are not. We live in a world of laws and relationships. Those also influence our development.
Most antisocial behavior is a consequence of one's developmental conditions. I believe most of it becomes fixed early in our development. Some of it is the result of an ethically ambiguous environment, or particularly strong formative events - abuse, neglect and such. But even in these environments most people still exhibit a discernable "moral compass".
Most of us in our adolescent years search for meaning and relevance in our lives, as we seek independence from our parents. Some find it in religious observance, others in other social constructs - law, philosophy, science. I was "raised" a Methodist, but outgrew the paternal and directive tenets of "faith". I found my touchstone in the law, and moral philosophy, which allowed me to shed the trappings of religious observance and focus on the ethical principles that undergird them (and many religions). I've found the tenets of
ethical humanism to be most profound and instructive.