I think most are self-interested twerps who are largely concerned with other people having "advantages" they do not have, while completely ignoring the advantages they themselves have had in life.
I'll bite, and hopefully won't regret it... I don't want to get into a big thing about this, but I would like to see if I can at least clarify for you why people think the way they do. (FWIW, I got in everywhere I applied, so AA didn't hurt me personally. Just so you know where I'm coming from.)
OK, so I think you acknowledge part of the problem people have, which is that a factor that one cannot control playing a big role in admissions. Reasonably smart people can work hard and get a good GPA and a good LSAT score... maybe not what they want, exactly, but at least in theory those are based on how YOU personally perform. Ditto for LORs, extracurriculars, work experience, etc. URM status is the one thing that the applicant has zero control over, yet it often has a huge impact.
But, as you say, lots of people have advantages they can't control: Wealthier people, for example, don't have to work in school, can hire LSAT tutors, grow up with the expectation of getting a good education, etc. So AA just compensates for that, right?
Not really. It's not like all white people are rich and all minorities are poor. Do you really think a black kid whose dad was a dentist should get advantages over a white kid who grew up in a singlewide? I don't. I would be more likely to support some sort of socio-economic AA than a race-based AA. I think it would give more real diversity than current programs as well as be more fair. If people actually have overcome a lot to get where they are, they deserve a boost.