To save you a click: the kind of diversity in question is "political or ideological diversity" with a focus on conservative politics and ideologies.
Conservative ideology is focused around defining progress (a term somewhat at odds with conservatism itself) as a return to a previous state of affairs (that may have never existed in the first place). That our civilizations apotheosis is somewhere in the past, not the future. This does not seem a compatible perspective with the idea of the university, which was handed down to us from the ideas of Socrates: to probe…
Because it sounds like a caricature that makes it easy to say "Oh yeah, of course we can't have these crazy conservatives around young people".