If atheists truly believe there are no objective moral standards, then how do they determine what's right and wrong, good and evil?

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It would be very helpful, for all concerned, if before leaving a comment you actually watch the clip. It's not too long, and it explains the point I'm making here, that no one can truly say that anything is right or wrong if there is no objective standard against which to measure the value of an action.
If atheists truly believe there are no objective moral standards, then how do they determine what's right and wrong, good and evil?
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