Some quick points.
I looked with curiosity to see if you would be the first atheist I'd encounter to finally offer a cogent discussion on where naturalistic morality might have come from.
This annoys me.
We covered this in our discussion. We derive the rules or codes of conduct that we might call morality by fleshing out the principles that we assume axiomatically. (Or at least, that's my view and the view I outlined in our discussion.) And you haven't convinced me that you don't need to make that same sort of move to flesh out a theistic moral system. You start from the assumption that there is a god and that this god is good. I start from the assumption that fairness is good.
And really, you've never made a convincing argument that theism can somehow ground a system of morality in a way that a non-theistic system can't.
Remember, on your view, all humanity is is a collection of self replicating fairly complicated chemical reactions. You know that fizzing stuff a bottle of coke makes when you open the lid too fast? We're a more complicated version of that - just a chemical reaction. Given that fizz has no moral duties and obligations (to borrow a phrase from Dr. Craig), can you show why humans have any?
I think this is a silly way of looking at things. It'd be a bit like saying that there really isn't a difference between listening to the sound of a jazz pianist and that of a jack hammer....after all, they're all just sound waves moving through the air. It's like saying that there's no difference between the Analects of Confucius and the Bible. After all, they're just old books. Just words on some pages. Or even better, it's like saying that there's no difference between a Bible verse and this:
It's all just characters on a page.
Murder, theft, and rape are evil.
Truth, honor, courage, and beauty are good.
The vast, vast majority of societies seem to agree on basic principles like these.
My grandmother was born in the 1920s, the same decade that the federal government had to take action to provide some level of legal consequences for the lynching of Blacks in the South since in the South, there were people that thought mutilating and killing Black people (paying careful attention to male genitalia of course) and then taking pictures with the corpse was just a swell way to spend a summer evening. And even then, this kind of violence against Blacks in the South still persisted well into the mid 20th century. In other words, not so long ago we thought murder was just fine every now and again. And there are people alive today that can tell you about it.
And rape? Homie, for most of this country's history, if a woman of color was raped by a white man she could be sure that her rapist would suffer no consequences. It didn't even count. Hell, for a lot of women, it didn't count until very recently. Did you know that it wasn't until 1993 that all 50 states recognized the crime of marital rape. This is something that hadn't occured to most societies as being a problem for a very long time. The prevailing view was that men were entitled to have sex with their wives by virtue of the fact of their marriage, whether they consented or not. And while we, being good and civilized people would tend to frown upon using rape in a military campaign, it was once a pretty common practice. I mean, in the 90s, tens of thousands of Bosnian women were raped during the war. In some places, the tactic is still being used--the Lord's Resistance Army in Central Africa as well as the Janjaweed in the Sudan come to mind. In other words, the notion that rape is always wrong is actually a pretty recent development and not one that has taken hold in every part of the world.
And theft? Nah, that's not even a universally agreed thing at all. I mean homie, we live in America. We live on land that was taken by force. (With plenty of rape and murder along the way.) There were even people that thought of this sort of thing as somehow God's will. On a more local level, I don't think that I'm the only one that bought a good amount stolen clothes as a teenager. One of my favorite rap groups, The Coup, has a whole song celebrating the people who steal from retail stores and sell to their community ("I Love Boosters"). In that case, we thought stealing was just fine.
I guess I should also say that the common thread in all of these cases is that, with the exception of marital rape, they're all things committed by one group against another. But that doesn't really effect the point that rape, murder and theft are not things that the vast, vast majority of peoples see or have seen as wrong in principle
or wrong in the way you're saying the Holocaust was wrong.
As for this:
Just so we're all 100% clear, you're saying Hitler was not wrong (because absolute wrongs don't exist) to murder millions of Jews.
I think it's kind of funny that you're pushing this point, given that you think that at least one set of genocides (the conquest of Canaan) was a perfectly fine thing. I mean, you seem to think that the inability of a non-theistic system to vigorously condemn the Holocaust is supposed to be a strike against it but all the while you affirm the goodness of a different genocide. Though I suppose you can ease your mind with the thought that it probably didn't happen. That the Bible is wrong about how the Israelites came to live where they lived.
In any case, I have a hard time seeing what you find wrong with the answer that these folks gave you.
(Had to edit that to complete a thought I left unfinished there towards the middle there.)