Morality

[Acrobat]

So, if you accept Plato's bit of wisdom here, then you may want to rethink the idea that only theists can be moral realists. 

Atheists can recognize the Good as well as any believer can. Some things might even work in the atheist's favor in trying to recognize the Good, such as not being bewildered by dogma. An atheist can search for the Good armed with only a sincere heart and mind. At the very least, I will say that an atheist is at no disadvantage when trying to distinguish the good from the not good. At the very least, they are just as able to distinguish an objective morality as a believer.

An atheists is a person who lacks a belief in God.

If Plato conception of The Good, constitutes as a God, than you can’t be an atheist and subscribe to Plato’s conception of the Good. Plenty of others, some even prechristian have saw the Good as such, like Plotinus, and Proclus, treating is as synonymous with conception of the One, and early Christian thinkers who have done the same. But I do think you’re operating on a false understanding of Plato’s form of the Good, that perhaps leads you to think otherwise

Edit: Since you also seem confused about what an atheist might consider moral facts, here is an argument I've put forth here before (from a paper found in the disclosed link):

I think there seems to be a number of atheists, since perhaps Harris who tend to see themselves as moral realist, but do so by redefining moral realism, or without ever acknowledging the ontological assumptions implicit in such beliefs.

You seem to be equating morality with explanations, as if morality or a moral fact is merely something descriptive, like stealing is bad, because it has x negative consequences, but this is wrong. Something being morally bad or good is not merely descriptive, it’s also prescriptive. A moral fact, needs to be both descriptive and prescriptive, or else it’s not a moral fact, it might be fact about a measurable degree of pain, or negative consequences, but not a moral one. Because morality not only describes how things are, but how they ought to be, obligations and duties to serve it.

Hence the reason why your explanation argument fails.

In showing someone why something they’re doing is immoral, I am not just describing what they’re doing and it’s effects, but also that because it’s bad they have a real obligation to not do it, not to me, or to society, but to The Good itself.

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A base of facilitating morality would be expected by evolutionary psychology.  That base has, for shits and giggles, been found and recorded.  All creatures with social structures and neurobiology meaningfully like our own have moral analogs such as taboo and exaltation.

Gazzaniga actually wrote a book about it, lol...and his most noted work is on the direct correlation between physiology and psychogeny and competence.
https://en.wikipedia.org/wiki/Michael_Gazzaniga

Acro's quote was mined, from a text arguing to the contrary of his point. The very next statements in the book that this quote is derived from, "Human"(2008) expound upon this.

Here's what I'm wondering...what trash website did Acro pull it from, and what was whatever shaman using it to say?

I quoted it, to highlight the lack of a relationship between moral reasoning and pro active moral behavior, not other components and proactive moral behavior.

It’s from page 148, here’s a fuller quote:

“It has been hard to find any correlation between moral reasoning and proactive moral behavior, such as helping other people. In fact, in most recent studies, none has been found,62, 63 except in one study done on young adults, in which there was a small correlation.64 As one might predict based on what we have learned so far, moral behavior, as evi- denced by helping others, is more correlated with emotion and self- control. Interestingly, Sam and Pearl Oliner, professors at Humboldt State University and founding directors of the Altruistic Personality and Prosocial Behavior Institute, studied moral exemplars by looking at Euro- pean rescuers of Jews during the Holocaust.65 Whereas 37 percent were empathically motivated (suffering module), 52 percent were primarily motivated by “expressing and strengthening their affiliations with their social groups” (coalition module), and only 11 percent were motivated by principled stands (rational thinking).”

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No, he’s referring to the effort to see The Good. And by this he doesn’t mean, that it takes such effort to see what’s right, but  the ultimate root, or source of such perception. Our perception of what’s right, is like seeing light from the sun, but not the sun itself, it takes considerable effort to see the sun.

“. It cannot be clearly seen or explained, but once it is recognized, it is the form that allows one to realize all the other forms.”

Non-natural realism.  That's usually where I start with realism no matter who's asking.  I'll even add the proviso that it doesn't always take great effort.  I arrange it in the reverse, however.  Let's you and I go watch the gang beating of a small child.  I wager that I won't need to explain anything at all.  The force of the observation will signify the thing we call "The Bad".  If we know "The Bad" - that which those terms signify, can see and observe and intuitively recognize it, then...by extension, we can understand the good (I'd make a second wager that the good and the bad, at least in archetypal forms, are equally recognizable). We can point at either representative and say "this, this is what I mean when I say x, do you understand?" - and the answer will be affirmative.

Again your talking about the light from the sun not the sun itself.

Confusing a concept relating to the ontology of Good, with epistemoloucal views.

It’s not about what’s right and wrong, as much as it is about what ultimately the root of right and wrong. A subjectivist might say it’s rooted in our own personal al feelings and opinions, like the our taste in food, or movies, a relativist might say it’s rooted in the collective opinions of our particular society and culture. While Plato would say its all ultimately rooted in The Good.