If you look closely at history, you will see what was before G-d (the Torah) was introduced. Look at the pagan societies of Rome and Greece and you will be appalled at the ‘morals’ they display. (Think Colosseum – go watch people fight to the death, insatiable bloodlust – constant brutal warfare, rampant infanticide, and if you are really interested read about their out of control activity in terms of Arayos).
To quote Aristotle “There must be a law that no imperfect or maimed child shall be brought up. And to avoid an excess in population some children must be exposed.”(ie killed)
Or Seneca who advocated maiming abandoned children so that people could laugh at them collecting in the street. (all with a justification – they would have been dead otherwise so we are making them useful).
Lest you think this is only in ancient times just look at the barbaric Indians in the Americas. The Aztecs – a highly advanced civilization that built amazing works and had advanced mathematics, calendars, science, etc. – had the most brutally efficient system for human sacrifice. They believed that the world would end if the blood stopped. So, they would go to war specifically to capture people to have a steady stream of sacrifices. (where they ripped their heart out). They were still doing this when the white poeple came over (only a couple hundred years ago).
Truth is you don’t have to look that far back to see where atheism gets you. Hitler, Stalin, Mao Zedong – this is what a state without religion looks like. Complete lack of regard for human life.
There is a general rule – Any civilization that has not been exposed to Torah you will find is a cruel, barbaric, immoral civilization.