The best counter-argument I have been able to formulate to this is that diversity would lead to temporary inequality, which is supposed to be alleviated. I think however that this segways into another argument I made some time ago, which is that the metaphysics of progressivism has no feasible end in sight, thereby robbing it of any concept of the peak of all things (God, etc.) and therefore making every extant and possible being an inferior to future beings, creating an eternal chain of subservients.
Although very subtle, I do believe that this metaphysical presumption is vaguely realized through progressive's growing totalitarian tendencies.
Le Fou Est Mort; Vive Le Fou!