When it comes to companies, diversity is far better than having whatever the equivalent of "everyone looks the same and has the same SAT scores" so presumably it'd probably work to Harvard's benefit as well to encourage diversity whether mandated by law or not.
There's been plenty of studies pointing to the positives of diversity. In order to foster an environment which will be diverse you're probably going to have to skip over some of the kids from the populations that are large and generally well off even if they have better SAT scores.
I personally, have no problem with this. The kid who just missed getting into Harvard because of their race is probably going to an awesome school and statistically is more likely to come from a pretty good place in the world. They'll be fine.
The other kids who do get in though, get to go to a school that is better precisely because of the advantages diversity offers.
Here's some reading:
http://images.forbes.com/forbesinsights/StudyPDFs/Innovation...