There are two stances that you are likely to hear on affirmative action at selective universities. The first is that it is flawed but necessary. The second is that it has the right goal but is the wrong method for achieving it. When debating the two, few people think to examine why affirmative action is necessary and the goals of those who institute it. The discussion only tends to go this far: Is the goal diversity? Does the black child of a CEO count? A poor Asian-American? A white kid from a trailer? What about the racism in this country that hits some groups harder than others? You are left with angry people on both sides, and are no closer to any solution, since you have not yet established what it is you are trying to solve.
Affirmative action, hardship points, and Texas-style top 10 percent programs, are meant to make selective universities' student bodies look as they would if all high schools in the country were the same, or at least equal in their ability to spew out good college fodder. This is what it means for colleges to create an equal playing field. In most cases, colleges themselves do not and cannot make students from all high schools equally prepared; the most they can do is provide opportunities--providing skills needed to make use of those opportunities is beyond the scope of a college. The playing field would have to be totally leveled in real life for there to exist college classes consisting of equally prepared yet diverse students. For a true meritocracy, not only must race not affect college admissions, but legacy, school district, parents' education, parents' interest in their children's education, and many other factors would need to be eliminated.
There is no way to know whether an intelligent 18-year-old who goes to a prep school and has educated parents interested in his education is smarter or more capable than another high school senior whose background is entirely average, or than one who has to overcome barriers simply to finish high school. Who knows, the prep-schooler might be a genius. It can happen. All that can be known is that being college-bound is easier for some than for others in the pool of those who are interested.
The admissions committee of a selective college must make estimates in order to establish things such as which students might have performed fabulously well at an academically challenging high school had they not gone to the prison-like one they actually attended. These estimates are destined to fail. A student who looks stellar could have spent his last 10 years being prepped by his school and extended family at how to appear stellar on a college application. A student who never took math higher than junior high level might be mentally capable of earning a Ph.D. This cannot be known.
Admission to selective universities hasn't changed since the candidates for admission were nearly all on a level playing field. Judging which students among several top high schools are most qualified to go on to a top college isn't especially difficult. Adding diversity of background means adding variables. A school that seeks out students from diverse backgrounds is not one that, to use a p.c. phrase, wishes to "celebrate" diversity. Rather, it is a school that wants to produce calculus-studiers, well connected networkers, and thesis-writers of all colors, shapes, and sizes. Selective colleges regularly produce people who are conventionally successful in mainstream society, which is nothing to sneeze at. Whether or not students benefit from being in a philosophy class with others from different backgrounds is not the main issue--providing opportunities for people to enter or remain at a certain economic or social level is.
If a level playing field among high schools did exist, if poorly performing high schools were somehow able to make up for lack of parental support whenever that was needed, and an individual student's motivation and intellect were the only factors determining his candidacy as an applicant, then a lot of people currently at top schools would be elsewhere, either at other schools or flipping proverbial burgers.
This is not about race. The upper-middle class white or Asian parents of a so-so student want their child to go to a good college, not to keep qualified blacks, Hispanics, and Native Americans out of the school, but because he's their child and thus deserves the best. The same goes for the upper-middle class black parent, etc. Each individual family wants their child to succeed, not as a representative of their race, but of their family. An unequal playing field of high school seniors is the direct result of parents, who have different capabilities and degrees of intellect, using their own strengths to do what any reasonable parent would and prepare their child to do well in the world as it is. This is a free country, and a free country cannot be a pure meritocracy. Meritocracy requires identification of raw talent, and by the time most of us reach our senior year of high school, our talents are at least medium rare.