@ joewaked

Hmmmm, the premises seem plausible to me. Nonetheless, given that Dave denies the PSR then I think your response works. I will add that if anyone denies the PSR then they can might as well reject philosophy and rationality. Let me quote Alexander Pruss from his "The Leibnizian Cosmological Argument" paper, "Is it morally acceptable to redirect a speeding trolley from a track on which there are five people onto track with only one person. On the other hand, it is not right to shoot one innocent person to save five. What is the morally relevant difference between the two cases? If we denied the PSR, then we could simply say: 'Who cares? Both of these moral facts are just brute facts, with no explanation.' Why, indeed, suppose that there should be some explanation of the difference in moral evaluation if we accept the denial of the PSR, and hence accept that there can be facts with no explanation at all? Almost all moral theorists accept the supervenience of the moral on the nonmoral. But without the PSR, would we really have reason to accept that? We could simply suppose brute contingent facts. In this world, torture is wrong. In that world, exactly alike in every other respect, torture is a duty. Why? No reason, just a contingent brute fact. The denial of the PSR, thus, would bring much philosophical argumentation to a standstill."

@DanielCC

Who do you think provides the best defenses or formulations of the moral argument? Lately, I've been thinking about the moral argument. Any recommended works would be of great appreciation. 

@ 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.  
 

Hi everyone,

I would like to pitch in my two cents. If ~PSR then brute facts. If this is the case then there is no point in asking why, its just is. Hence, one stops looking for metaphysical answers and becomes cynical. Teleologically, one frustrates one's rational intuitions, as aftermathemat said.  

Hi Dry and Uninspired, 
I'm not sure if this will help, but have you brought up atheist to theist conversions? For example, have you told them how Dr. Feser changed his mind due to natural theology arguments? What about one of atheism"s strongest defenders, Anthony Flew? You could also mention Dr. Sarah Salviander (An astrophysicist and a Christian). She was born and raised in an atheist household, but became a theist when she studied astrophysics.