Haidt, in his great book "The Righteous Mind," has been arguing that reasoning evolved not to discover truth but to win arguments. There's a lot of scientific research backing his idea.

Haidt's metaphor is the rider and the elephant: the elephant (intuition) leans, and the rider (reasoning) invents the justification afterward and then defends it like a lawyer, not a truth-seeker.

Intelligence doesn't fix this - it just makes people better at coming up with hard-to-defeat arguments; that explains why smart people disagree all the time.