I had to write on the same topic when I applied to NC State as an undergrad; I basically said that "diversity" is a vague notion in that it does not specify what should or should not be diverse (skin color, religions, ideas, shoe sizes...). I then said that the standard attempts to create a "diverse campus" were, in effect, racism and that it was the content of a person's mind that made them who they were. Over and above that, I think I indicated that even intellectual diversity was not a good thing as such and that truth should shape the ideal climate of a good university.
Whatever, I was 17. I was accepted, btw.