I never had to take an diversity classes per se, but since I was a Psych Major I guess their was no need. As a multi-racial person, I see the need for these classes, but not the effectiveness. As is with case of most sensitivity/diversity training, the people who need it the most will be the ones with fingers in their ears and feet their mouths.
Let me digress. . .
On our campus a group of student media leaders (TV, radio, and print) put a very anti-semetic/anti-arab slant on the school newspaper ( this was pre-9-11). Unfortunately for them, we have a very active Muslim- student association. They brought a 500-page list of articles, evidence, and grievences against the newspaper. The gulity parties were sentenced to sensitivity training. Do you think they have changed? I doubt it.
Digression over.
The best way (albeit very slow) for people to learn is through experience and exposure. If people have positive interactions, with a group they have negatively stereotyped, then change might happen. Apparently, the university can't make this change happen fast enough and these classes are the result. But, the most likely course of action, is that people learn the hard way. When patients or co-workers complain about your off-color jokes, or when you are taken aside by a supervisor told that others would rather not work with you, you will learn.