Atheists do not have morals.
They have opinions.
Atheists have preferences.
They know what they like and they know what they don't like, but beyond that, in atheist-world, it all comes down to one's opinion. And more to the point, it comes down to which opinion belongs to the atheist(s) with the most power.
On atheism there's no such thing as evil because the perception of evil presupposes the existence of objective good. As C.S. Lewis said, “You can't know that a stick is crooked unless you have a straight stick against which you measure the crooked stick.” You can have good without evil, but you can't have evil without a base of objective good.
In fact evil is simply our decision to reject that which we know to be objective good. That is why atheists are wrong when they say that the existence of evil disproves the existence of God - or even - the existence of a God who is good. There wouldn't be a knowledge of evil unless there was also a standard of good, and there would not be an objective standard of good unless Creator God existed.
Now, atheists call their opinions their moral standard, and atheists are free to HAVE something they call a moral standard. They simply can't justify on a logical basis why their opinion is better than the atheist who disagrees with that opinion. As I've said many times, In atheist-world, if you say you have one unit of value and your neighbour says you have no value, your neighbour is just as correct as you are.