For us basketball fans, imagine a world in which we didn't get to see the very, very best but instead the players were apportioned by race - there'd be the requisite asian, x whites, x hispanics and ONLY 16% blacks. In this world, we would only see Lebron, Durant, Davis, ... the very top players - we would not see the black players who even though they were better than the asian/white/hispanic players couldn't play because of AA. Fortunately for us, in a free market system we get to see the best based on merit not race.
If you had to have brain surgery done (Ben Carson notwithstanding), would you prefer the very best surgeon based on merit or one who got in because of AA (med school admission accepts blacks with lower MCAT scores and GPA than white/asians).