People are born with an innate capacity for social reciprocity and emotional connection. If raised by good parents, this in most cases is enough. My parents didnt need to say to me, "You better not kill someone because God said so" My innate capacity for social and emotional relationships, coupled with good parenting is more than enough to make me a good citizen. To believe otherwise is the bible brainwashing you into believing that if someone doesnt say to you "god say dont do that" youre going to kill 500 people 
What you have to realize is everything you just said is relative to a Christianity based society that you, your parents, your parents parents,etc were raised in. So much of what we think to be morally right and wrong in the US and Europe has been built and shaped around christian beliefs over the past thousand+ years. So much so that our very thoughts are hard to separate from Christan rooted principals.
If you were raised about 1,000 years ago in say...um South America, your exact views would vastly different, since the entire concept of morality, what is right and wrong, etc would be vastly different. They did human sacrifices and thought it wasn't just OK and right, but a needed necessity to make the SUN gods happy and help bring on a good harvest season. If we were to speak to those exact individuals they might look at us as crazy in how sensitive we are to killing.
Goes back to what Chiro Flex was saying about moral relativism.
