Why is diversity a moral attribute?
In the moral system that my readers and I inhabit the ultimate moral criteria is whether individuals are able to develop their unique capabilities in the most effective and complete manner.
In a system that values diversity we have to have mechanisms that protect a very wide range of values attitudes and behaviors. Here in San Francisco we can have an extreme range of behaviors that are tolerated in a way that would be impossible in Isfahan.
A black man in drag can walk on the street with two Asian women one of whom is wearing a bathing suit with tattoos. That is actually mild for San Francisco. It is also only a reference to external attributes. Genius and weirdness are also tolerated in a diverse society.
Meritocracy is also a moral attribute in our system of values. It is only in a society where individual uniqueness can be recognized and appreciated, a meritocratic society, that the uniqueness of individuals has a chance to be triumphant.
Openness is a traditional moral value. It is biblical. It is important because secrecy and dishonesty that can be covered by secrecy are the source of a great deal of social malice and bad moral behavior.
Commerce, because the attributes that make it thrive are moral, is a moral system.