For all practical purposes, about 30% of people are unfeeling morons - basically psychopaths. That’s the number that consistently opposes abortion, for instance. Add to that all the dumbasses who don’t know any better (the undecideds on any extremely obvious moral issue), et voila. That’s how you get slavery, nationalism, genocide, theocracy, you name it.

Unless people are willing to screen for psychopathy and remove it from the gene pool, the human species will keep fucking around until it finds out. Might be nuclear apocalypse or environmental collapse, but at this rate it’s inevitable.