"Two things are infinite: the universe and human stupidity." — Albert Einstein
"The greatest threat to humanity is not evil, but stupidity." — Yuval N. Harari, Nexus
Stupidity is a main factor in injustice, violence, wars, prejudice, hatred, denial of reality, superstition, environmental destruction, economic inequality, health inequality, social division, intolerance, and most ailments that empoverish humanity.
It is often the most unassailable obstacle against general human wellbeing. As the Latin saying goes: Inermes contra stultitiam: "Nothing can defeat stupidity"—by definition, stupidity resists reason.