Here’s excerpt from that article in Heterodox Academy (an organization founded by Jonathan Haidt):
we again replicated the positive relationship between cognitive ability and supporting freedom of speech for all groups across the ideological spectrum.
Moreover, … we found evidence that higher levels of Intellectual Humility could explain the relationship between cognitive ability and free speech support. In other words, those with higher cognitive ability might support principles of free speech because of their greater independence of intellect and ego, openness to revise their viewpoints, respect for others’ viewpoints, and lack of intellectual overconfidence.