They simply have to have faith that everything they say is true.
Oh, and to add to it being a “sin nature” thing, not isolated to any faith or lack of faith -
the closer one is to one’s sin nature and the further one is from the Spirit of Truth,
the more likely they would be to engage in arrogant, condescending, insulting behavior.
After all, the very first sin was the temptation to be like God. And I assert that atheists are “gods unto themselves”.