So? If that is true, it is still a result of life coming from nothingness/no life, by chance, going back into nothingness.
In that world, whatever you call "morality" has no essential importance and is just a byproduct of meaningless existence. Other people have different "morals" than you, and their positions are just as valid.
Size of the group in such universe, or any other quality, doesn't make it's values any more valid. Because there is ultimately nothing to be valid about.
If thousand people full of hate and thirst to kill somehow end up destroying seven billion, that is still perfectly fine in atheistic universe. Those thousand people are not bad. They got to exist just as you, by chance. Everything is by chance anyway, enclosed by nothingness, with no universal law that says, for example, that small group of people must not overpower large group of people and that it is bad if they do.