Why is this argument not used in promoting minority rights?

Those who argue in favor of minority rights talk in terms of fairness and unfairness. This is a valid argument, but there is a larger point that is being missed and which could provide strong motivation for non-minority members to support minority rights.

By restricting the eligibility of those who can serve office or who have a sufficient education to reach their full potential, we are also restricting the pool of competitors for any given position. Simply put, there is a good chance that the person who is most qualified will not be given a chance. Now it becomes more than just a minority issue. It is an issue for society at large.

Sometimes diversity is given as a reason for minority rights. This a good argument, but it does not go far enough. Diversity is fine, but it is also true that diversity leads to greater choices and a better chance of choosing the best person. For example, baseball improved overall when the first black players were hired. We can go into an extended argument as to the specifics as to why this is so, but it remains a fact that, in general, diversity leads to improvement.