there is no justification for morality if there is no God. There’s no reason for it.

Care to elaborate on this? Specifically, what reasons/justifications are there for being moral, assuming one believes that gods exist, and how would those reasons be different - or why would they not exist - for people with no knowledge of the concept of gods, or belief that they exist?

I ask this question assuming we are both aware that there have been many diverse populations of people on Earth for hundreds of thousands of years, many of which existed long before the modern concept of gods, and many with faith so strong that they would ritually abuse and sacrifice children, or blow themselves up in crowds of people, and I'm hard pressed to find any moral consistency among them that makes one group and their gods better that another's, or lack thereof.