People who get all tied up in knots about URMs/AA remind me of geldrop complaining that rolling admissions is unfair, basically because he didn't get in.
The point about legacies/connections advantages should not be taken lightly. AA was started because several decades ago, folks looked around and realized that the white majority in this country does tend to have a huge amount of advantage in procuring education and jobs, and that this did not seem right. Some would even say it is 'un-American'. While it is improtant to note that class does not equal race, at that time, being black or hispanic went largely hand-in-hand with being fed a lot of disagvantages pretty early in life. I am NOT saying that there weren't poor white folk - just that anyone with darker skin was facing a much bigger struggle than a whitey.
Fast forward to today - some people think that the time for such a leg up for some folks is over, that we have acheived a society in which such problems need no longer be adressed. I would say that's wrong. Take a look around the NYC school system, for example, and you see that the racial make-up of the schools with the worst records, lowest funding, and most overcrowding tend to be clustered in 'minority' neighborhoods and full of 'minority' students. SAT prep classes, and, later, MCAT prep classes are full of the people who can afford to take them. Its a lot harder to make yourself a competitive applicant, with a 3.9 GPA and thousands of hours of volunteering if you are working your way through school.
Not all of this correlates with race, of course. For me the equation is more of an economic one, and I would be more comfortable with a system that could take into account economic and cultural factors in someones background as well as their skin color. But my point is this: we live in a society that is inherently unfair. Some of us are born with advantages that others will never have; some of us start out with the deck stacked against us from the first smack on the bottom in the delivery room. The AA system was designed to try to correct for that. Is it perfect? NO. It has problems that still need to be fixed. But a complete scrapping of it would only be a huge leap backwards, in which legacies and 'buy-ins' (which are much more common than you think - I personally know three people whose med admissions may have been legacy admits, and one girl who 'bought' her diploma from my undergrad with a donation from daddy and made no bones about it) would remain o.k, while any consideration of a disadvataged background would not.
In a process as subjective as medical school admissions, there will always be questionable decisions made by adcoms. And there will always be those left out in the cold looking for a scapegoat for their failures. We freak out when we are on the bad end of an unfair process, and excel at turning a blind eye to all the unfairness that surrounds us that works to our advantage.
Anyone interested, there was an interesting little piece in the Nation a few weeks back about how race figures into SAT test question selection - sorry, no link, but it might be on their website if you look it up.