Mass society breeds mass insanity
The opposite of mass society is communitarian society.
In the latter people live in human-scale units characterized by familiarity and local interdependence. Under those conditions of life you’d never see things like homelessness or extreme class disparity.
Mass society breeds mass insanity. An example of mass insanity is war.
Most of the Indian tribal societies were communitarian (prior to the trauma of the Columbian climacteric). The tribes skirmished, essentially to establish and maintain territorial boundaries. There was some loss of life, but they did not wholescale kill each other. The only ones who did were the few that effectuated the unfortunate transition into mass society (Aztecs, Incas).