But 1) God hasn't commanded for or against all human acts. So how do we know which are right or wrong?
So the "God commands it" answer to the wrong-maker question seems pretty useless. Even Christians are forced to use their own judgment when it comes to modern day moral dilemmas; God is of no help to them. The Methodist church recently had a schism over gay marriage.
And 3) Doesn't this open up the Euthyphro Dilemma? If the right-maker is purely God's command, then God could command E and that would make E right. But my intuitions say, like that of Christians, that a good God could never make such a command because the act is wrong prior to any command made for or against it. So it must be something else that acts as the wrong-maker.
b) If goodness is defined as that which is aligned with God's nature, then saying "God is good" is to say "God is aligned with God's nature", which is a silly thing to say. But Christians don't see themselves as saying something silly when they say "God is good."
c) We call things good all the time – good friends, good food, good movies – without invoking God. These things aren't good because they are aligned with God's nature – they are good because they are intrinsic, extrinsic, or saving goods.
Second, I say again that the badness of E is easy to see, no God required.
1) We can give a phenomenal definition to intrinsic goodness and badness. Intrinsic goods are characterized by their felt experience, same with intrinsic bads (evils).
2) Extrinsic goods are those that lead to intrinsic goods. Extrinsic evils lead to intrinsic evils.
3) Saving goods are those goods that prevent evils. Depriving evils are those evils that prevent goods.
And so by this analysis we can easily see what the bad makers are of E. The intrinsic evils of the suffering of the victims and victims' families are bad in their essence. The depriving evils of the deaths of the victims are bad too, grounded in the self-evident concept of "better" as used in the sentence: A joy feels better than a pain.
Now the wrong-maker is trickier. A consequentialist approach could be like this: The act that produces the worst outcomes (most badness + least goodness) in a situation is the worst act, and the act that produces the best outcomes (the least badness / most goodness) in that same situation is the best act.
Assumption 1: There is no difference whatsoever between epistemic and value-based wrongness. Both amount to being incorrect or mistaken in some sense.
Assumption 2: Every morally relevant act is caused by a belief or set of beliefs, or something like a belief that could be translated into a proposition.
Idea: The wrong-maker of an act is the falsity of the false belief that grounds the act.
People often (always?) act thinking that their action is the best action they could take, the action that maximizes goodness over badness. If that belief is false, then the wrongness of that belief transmits to the action, making the action wrong too (strictly speaking, there are no wrong actions, only wrong beliefs and bad actions).
He who succeeds in believing what's right will act rightly too. There are no categorical imperatives, only hypothetical imperatives: If you want to believe what's true, and act accordingly, and if you succeed in always believing what's true and acting accordingly, then you will never do wrong. Your actions will always be grounded in true beliefs.
If you want to do what's right, then you should act according to what's true – and there we see the hypothetical imperative. "Should" always applies to goals – given the goal of doing what's right, you ought to believe what's true. If you want to maximize goodness, then you ought not commit acts that fail especially badly to maximize goodness (which we call evil acts).
Of course, we humans are ignorant and stupid, and so we constantly fail to believe what's true. So we constantly act according to false beliefs and do actions that are bad. (And our answers as to why we chose to do these bad actions are always filled with lies, falsehoods, contradictions, confusions, or irrelevancies).