But it all relies on assuming he is in fact speaking from a non-religious viewpoint.
The writer is writing from a religious or non-religious point of view. Which is more likely? In view of his phrasing, I'd say the latter. More personal info could tip the balance the other way, however.
Don't mean to pee in your cornflakes, but it sounds to me as though you're trying to use Big Words and Big Ideas but still aren't saying much of anything.
I use Big Words and Big Ideas so you will think I'm the most awesome anonymous writer you've never met.
I'll boil the winding prose down to four lines each written in small words:
1. If God is not real then there are no moral facts.
2. There are moral facts.
3. God is real.
4. Every non-religious worldview is false.
Do you honestly believe that one cannot separate morality from religion?
Let me put it this way: atheists can be good people but the term "good" is only meaningful if God is real. If he isn't real then saying someone is good is at best like saying you so happen to like them, which is still no more significant than saying you like chocolate ice cream.