Explain the doctrine of enlightened self-interest as it applies to stockholder interest

Another argument for social responsibility is that it is in the interest of the stockholder for business to engage in certain kinds of responsible behavior. Of course, this argument applies to such concepts as public image and avoidance of government regulation, but economist Henry C. Wallich also shows that it applies in a strict economic sense to stockholder. Corporate activities which would not be worthwhile to a stockholder in a single firm definitely become worthwhile to a diversified stockholder. He shows that types of responsible behavior which bring returns to the corporate sector as a whole actually operate to the benefit of the holder of a diversified portfolio.