Or an accepted transcendent moral standard by which things are judged. The supreme moral reasoning of one atheist can conditionally justify fornication, while another can argue against it and for marriage..
Both assert this is consistent with the Golden Rule, but which itself presupposes a foundational morality, in the light of which what you would have done unto you is determined. Thus in Scripture it is the second great commandment, after love for God, which entails obeying what He wrote.
Target hit on the above. In the state debates of posting the 10 Commandments in public places, some take the "middle road" and just want to place the ones that are not "controversial." Meaning even some atheists see "goodness" in teaching "do not kill; do not steal; do not lie" but think addressing things like covetousness and adultery are too "judgmental" to "preach." Then of course you have the Commandments dealing with our relationship with God are first and which establish the Holiness of the remaining commandments which address our relationship with fellow man.
So yes, they reject the "transcendent moral standard by which things are judged."