What is an absurdity? It is something that is not believable IF you are
paying attention and thinking it through. You have to purposely ignore
evidence that is easily in reach and you have to have a pre-existing (even
if unconscious) desire to believe the absurdity for it to persuade you.
How does it lead to atrocities? If you believe, as people of many races
have over the centuries, that people of other races are not fully human,
then denying them rights (or killing them) is easily rationalized.
If you believe, as people of many religions have over the centuries, that
people of other religions are eternally damned, then treating them as
less than human (or killing them) is easily rationalized.
If you believe, as people of many political persuasions have over the
centuries, that those who don’t believe in the same way of governing
as you do are evil and corrupt, then keeping them from being politically
involved (or killing them) is easily rationalized.
If you believe, as people of both genders have over the centuries, that
women are less intelligent and able than men, then oppressing them
(or killing them) is easily rationalized.
Where did those actions come from over the centuries? From believing absurdities.
“Those who can make you believe absurdities can make you commit atrocities.” – Francois-Marie Arouet (Voltaire)