This all seems logical until one asks, "How does something come from nothing?"
This question is in response to the article, "Where does morality come from, if not God?"
You should read the article, "If there is no god, how do you explain _______?" - it's the same basic error in reasoning.
Also, this all seems logical until one asks, "How can a brainless mind that exists outside of existence speak/think existence into reality?" Believe it or not, but the generic theistic position has more absurdities added than simply something coming from nothing.
Then again, that's not even my position, nor is it the position of virtually all atheists. Why do you think it's only a choice between a god and nothing? Is "we don't know until there's sufficient evidence" not an option? It could be that the actual answer is something we haven't even thought of yet.
Whatever someone proposes as the explanation of the universe had better have evidentiary backing, before it's logical to accept as true.
Your question doesn't even affect the basis of morality. If I can reverse engineer an alien engine, and figure out how it works... I don't need to explain where that gasoline came from in order for the understanding of the engine mechanics to be justified. Nor do I need to explain the origins of life, nor the origin of the planet, nor the origin of the solar system, nor the origin of the galaxy, nor the origin of the universe.
Demonstration that hyrdocarbon liquids exist, is sufficient. It's the most recent demonstrable link on the chain of causality.
So yes, even without any knowledge about the origins of the universe, our understanding of morality is logical. I'm not sure how you get from A to B on that.