1) The 20th century saw the rise of secular humanist states that were responsible for killing over 180 million of their own people, far more than all other religions combined or wars.
2) Communist regimes in the Soviet Union, China, Cambodia, and other countries were responsible for the deaths of over 100 million people through executions, starvation, forced labor, and concentration camps.
3) The collapse of religion-based morality in secular states led to moral relativism and view of humans as insignificant, contributing to devaluation of human life and mass killings under these regimes in the name of ideology like communism or progress.