Also, why NOT measure "diversity"? You don't have to act on it, but it sure would be nice to have the metrics for any later analysis. It's not hard and isn't something that takes many resources to compile.
It's not arbitrary. The gender and ethnic makeup of the tech industry are significantly divergent from the general population, and there is no job-performance reason for it.
It's not like it's the NBA, where you have to be a tall strong man to make the team. Anyone can program, market, manage, etc.