Certainly all the clones looked alike. Maybe that somehow encouraged a culture of racial preference leading to prejudice in the military, which persisted even after the clones died out.
I asked what the assumption of species homogeneity in the Empire was based on, because the only Imperial institution we get a good look at is the military. The Senate was dissolved. We only get a glimpse of the Emperor's court, in ROTJ, but they aren't human.