I think somehow it's based on the idea of "give more opportunities to the weak" which seems more humane.
It's not the policy only in the State. Believe or not, there's a similar policy in China that if a student is ethnic minority then s/he can get extra scores on the university entry exam named GaoKao which is equivalent to SAT. To take advantage of the preferential treatment, there are quite some fake "minority" students who might have some blood of ethnic minorities. The favorable treatment is not limited to GaoKao.
Personally I'm not totally against the policy in general. It's true that weak groups need to be taken care of. But there are many problems:
1.It doesn't reflect the real academic capability for the students who got extra scores. Eventually some of them can not catch up the pace of normal courses.
2.It created another stereo type and bias towards those students. The are considered to be less competent but actually some of them are excellent.
3.There's no social problem like eastern Asia countries that the minorities are very small group. No body complain. In US it's a totally different situation that could cause tension.