Mysterious Brony wrote:

@ Dry and Uninspired 
Hopefully their hearts become unhardened. 

 
Thank you. I hope so too.

@ joewaked

I'm going to pitch in my two cents. 

"If so, how do we develop the argument for his moral goodness?   I’m currently stuck in my explanation of how/why God must be morally Good."

I'm not exactly sure what are you asking. However, I will give you related answers. Since God is Goodness Itself then from His Nature (which is His Goodness) "flows" the good. More specifically, God will necessarily (meaning in all possible worlds) give out good moral commands and command avoiding evils.  
 

@ joewaked
I think I understand what you are asking.

In a way, yes, God is "possession of all perfections."* Let's remember that God cannot lack "perfection" or else He's not God. Since that's the case then yes, such "perfection" necessarily includes moral goodness. 

*As a side note: This can lead to semantic-ontology questions. 

I have seen it argued that God is not morally good because moral goodness is a property of persons, and God is not a person. God is not held to have duties or obligations.

It's because goodness is convertible with being. That's the traditional doctrine of the convertibility of the transcendentals: being, truth and goodness. Read the relevant passages in Five Proofs for it, and/or the chapter on the transcendentals in Feser's "Aquinas". Briefly, though, take the example of triangles: a carefully drawn triangle made with rulers and pencils is closer to a perfect representation of triangularity than a shitty triangle hastily drawn on the seat of a moving bus. The first triangle is, in this sense, a "truer" representation of triangularity, since it approximates it more perfectly, whereas the second one has many accidents which deviate more from a perfect representation of triangularity. In this sense the first triangle is also a better (more good) representation of triangularity, while the second is a worse triangle. There is, therefore, a kind of convertibility of truth and good into being; in the case of truth it can be even clearer because what is true is that which corresponds with reality (correspondence theory of truth), when we have a hypothesis about what our bodies are composed of (for example) we want to confirm it by investigating bodies and finding out whether what our bodies are made of *is*/*corresponds to* that which our hypothesis referenced, in which case the hypothesis is taken as true. Goodness is included too, since a true hypothesis -- that which corresponds better to reality, to what things are, to being -- will be a better hypothesis than a false one, and will as a result be a *more desirable hypothesis*. We can say good is being as desirable.

A fact I find very illuminating for the mutual convertibility of the transcendentals is how truth itself is good. Truth qua truth is essentially desirable. And no one can rationally deny they desire the truth. Likewise, no one can rationally desire a good which is *not* true, a false good. If we know such a "good" is false, then it is irrational to desire it. I then argue that since truth is good, and truth is being, then being is good. And I think the "good" in truth is already something much closer to moral goodness than the goodness in a more accurate representation of a triangle.

Natural law can also be helpful for showing how being = good, especially in the moral sense, so you can check that out. But anyway. Considering the convertibility of the transcendentals, since God is Pure Act, Existence itself, Absolutely Necessary, absolute being, etc., then He is also absolute goodness (and truth).

That being said, there are other ways to show God is morally good, I believe.

One argument I developed is that if God is omniscient, then it is very plausible that he is perfectly virtuous and morally good. First, consider that omniscience can be derived from omnipotence (if a being is omnipotent then he can know all there is to know, of course) of the first cause; or from an argument such as the Augustinian proof, or from teleological arguments. But now, knowing what we know about morality, how likely is it that a supremely wise being could fail to be perfectly good? How can a truly wise being (let alone a supremely wise being) not be virtuous, not seek what is good, or be fooled by lower passions or corruption? It's absurd. We recognize that true wisdom walks hand in hand with moral goodness and virtue. A being who is omniscient or perfectly wise cannot fail to be perfectly good and virtuous.

(I believe we can also lower the requirements a little if needed; if someone is struggling to demonstrate omniscience. As long as a being is very intelligent/wise (which seems to follow almost immediately from most arguments for God's existence, cosmological teleological augustinian etc) it will be plausible that it is also morally good. Someone who is intelligent and wise should be able to recognize what is really good and not be fooled by false goods.)

A second argument I developed would follow from the Necessary Being's free will; since creation was free (as there are contingent things), the necessary being could have chosen not to create, but chose to. Why? In a way, it must imply that the Necessary Being sees something of value in the universe, loves it, etc. If this being is loving and loves a universe with us in it, then this is already relevant to establishing its identity with God, but specifically it can also point to moral goodness since love is good.