Once your faith, sir, persuades you to believe what your intelligence declares to be absurd, beware lest you likewise sacrifice your reason in the conduct of your life. In days gone by, there were people who said to us: "you believe in incomprehensible, contradictory, and impossible things because we have commanded you to; now then, commit unjust acts because we likewise order you to do so."
Nothing could be more convincing.
Certainly, anyone who has the power to make you believe absurdities has the power to make you commit injustices.
― Voltaire - Question on Miracles (11th Letter), 1765.
Garry Kasparov tells us ...
This is why dictators and would-be autocrats push conspiracy theories and misinformation. They wish to weaken the mind and to spin the moral compass. The truth is always their greatest enemy.
It's not satisfactory to simply say that all those who do evil acts are evil. It has a beginning, nearly always with believing falsities and absurdities peddled by the power-hungry. The truth is the first casualty, and never the last.
When a leader lies constantly, the goal isn't to make you believe something; it's to make you believe anything.