No, actually it makes more sense for universities to accept the best students. And yes, there is actually a very good reason to accept that black guy. As someone who has actually worked in university administration, I will tell you that the university's mission is to educate students and produce scholarship. Both suffer if you have dreary homogeneity of thking and approaches. So, if you develop a student body and faculty that have a wide variety of perspectives and approaches, all students benefit.
Also, Chaga, keep in mind that universities are public or non-profit institutions. They aren't out to make a buck, so money isn't that much of a consideration frequently and shouldn't be. If we want soulless mindless dead institutions, we have corporations for that. Universities are trying to accomplish something entirely different.
(Also, keep in mind that places like Ivy Leagues could pay the tuition for the ENTIRE student bodies with a few weeks of interest on their endowments. Also, the tuition is largely paid by loans these days, so the universities get their cuts regardless. )