As long as you are moral, it is okay not to know. As long as you are just, it is okay not to believe.
That sounds awesome, and I kinda agree with it, but allow me to present a specific, extreme example of differing morality.
I think that the sanctity of life comes above all else. Taking a life is permissible only to ease pointless suffering at their request or to save other lives.
I know someone who believes the white race comes before all else and if all non-whites can not be expunged from the US, it is completely moral to exterminate them. He'd rather not kill them all, but he believes it would be moral. Put another way, it would be moral under his beliefs.
Morality is way too subjective to even count that alone as the deciding factor if there is a God watching.