You may never find the common ground that allows you to understand all of why your opponent on something approaches the situation as he does, but you do need to let go of the idea that he does what he does because he is stupid or evil.
Let go of this so that you can move forward from a position of greater comprehension about the situation as whole.
Let go of this so that others – opponents, allies or observers – are less inclined to see you and your viewpoint as naive.
Let go of this so you are more open to a successful outcome.