People are not bigots because they cannot reason, but because they have learned to hate and have contempt on the basis of group membership.
Their behaviors and thoughts seem irrational because they are. Emotions are by definition not rational, and they are using an emotion state to drive their behavior. Because it benefits them and ultimately feels good.
That's why the way to counter it is to socially deflate that good feeling, the gratification resulting from acting on bigotry.