Nietzsche in a cowboy outfit for some wonderful reason
The people I know who do not believe in god tend to wind up with the same ethical systems as the people who do. Maybe it’s the beneficent influence of a traditionally religious society; maybe it’s biological, but people of all creeds enjoy consensus on basic altruism. You don’t need the Bible to tell you stealing is bad, for the same reason that you don’t need a referee to play backyard football. Ethical systems are based on actions, results and sometimes motives. Provided they agree on what’s right and what’s wrong, two ethical systems can be functionally congruent while totally disagreeing on why wrong is wrong and not right.