"Good Without God is 0?"
Theism as constraint on humans murdering other humans stands refuted. You could of course add the proviso that the deity in question is a "good" deity, but here is the paradox. Who defines what is good? If you are a theist, god defines what is good. The followers of Huitzilopochtli were following the good according to their deity. Who are we to judge them if we say that theism is the best grounding for objective morals? But if you don't believe all religions are the same…by what criteria are you judging?
If theism is the basis of morality, "good" and "bad" have only whatever meaning a particular religion ascribes them. "Good" is whatever god commands. This is moral relativism. And claiming that one's own religion is good doesn't save one from the problem since of course one must believe on the theistic view that one's own religion is good. Furthermore, if you make any claims to know that your religion is good beyond the fact that it is defined as good by your religion, you must justify that with secular morality. The whole thing is a self-refuting conundrum. You cannot appeal to your own chosen brand of theism. That way won't give you objectivity that is in any way more objective than the Aztec's. The Aztec would apply the same internal circular reasoning and appeal to his own theism to say why you are "objectively" wrong. And the crux is this, we need a more objective standard to distinguish which one of you is correct. We need a standard that does not appeal to theism. Because the Aztec and the Christian equally adhere to theism; both define good in terms of what their god commands; and both believe with conviction that their way is correct.
One thing the theist must concede is this -- theism as a basis for morality does not consistently lead to human flourishing. It can lead to massive suffering depending on the theism one chooses. Theism as our sole basis for what we shall call "good" is not an effective method of increasing human flourishing and diminishing suffering. It's a gamble. If you choose deity x, you think ripping out hearts is good. If you choose deity y, you think ripping out hearts is bad. This really is moral relativism. The view that good is whatever the god you choose commands -- this is moral relativism. You do not have an objective standard for judging which particular theism is correct. If you are a theist you can only judge from your own theism. The Aztec believes he is correct. The Christian believes he is correct. How would an outside observer go about deciding which of these two "objective" moral systems is better?
I am unimpressed when people appeal to their religious bias to justify their religiously grounded beliefs. It's called religious bias. This is not objective morality. The Aztec or the Druid believed just as sincerely that their theism was correct and would have appealed to their theism to justify their beliefs about slaughtering people.
We need a more objective standard by which to judge which theism is better or worse for the health of humanity. We need secular morality. We need a morality based on reason and empathy that has as its aim the flourishing of human well-being and the diminishing of suffering. This can be accomplished through education. Why would we want this? Because it's rational. Because many of us would like to see the species survive long enough to make it to the next star system. Because we have a desire for our own survival and that of our loved ones and community. It is built into us. And we have learned that expanding the circle of sentiments to include other more distant neighbors is a better strategy than perpetual conflict. Reciprocity, cooperation, and the sharing of ideas and resources is an effective strategy for survival. And we have become one community because of our technology and expanding populations. It is more important than ever now that we cooperate if we wish to avoid destroying ourselves.
Good cannot simply be up to whichever theism a person arbitrarily believes in. And if you say you believe in your particular deity because it is good, stop a moment to consider. By what standard are you judging that your deity is good?
If you joined a church or Hindu temple because you thought the beliefs of that church or temple were good, by what standard were you judging?
On the other hand, if you believe in a religion because you were raised in it, consider what you might have believed had you been raised in a different religion.