Gradually their numbers increase and their portions of the Earth become larger and more poisoned. Their own spirit recognizes this and so their culture becomes more destructive, raging at the planet which denies them, killing themselves off because nature demands it. Warfare becomes more frequent, easier to provoke. Patriots are vilified, alternative beliefs are ridiculed, enforcement and punishment is glorified. The television routinely shows police using force in positive light.
Disgruntled teens go on school shooting sprees and nine year olds bring weapons to class.
One kills a six year old. The forces of coercion demand and reveal their easy solution - more control, more police presence, more escalation. One interpretation is that nature is doing it's own population control. Passive means such as increased rates of homosexuality have not slowed the population trend enough. So the human race begins to actively self destruct.