But surely uniformity is a desirable thing. It would eliminate the injustices which come with differentiation!

Uniformity was in the beginning and since then the whole evolutionary drive spiritual and physical, has been towards divergence and differentiation. Those who proclaim the desirability of uniformity turn away from progress, they are heading in the wrong direction. Everything in Nature proclaims that uniformity is not the objective and that the drive should be towards individualisation. The lower on the evolutionary scale a thing is, the more uniform it will be.