thank you.
Inequality has always been organized by categories, mainly b/c it's easier to organize coalitions and distribute resources when individuals are clearly marked into groups. the relevant categories shift, but the pattern has always been the same.
Race has become less relevant as a category than it was in the 1950s, but it is still enormously important in America. This categorical inequality works in favor of whites relative to nonwhites in almost every way, from childhood to adulthood. It is not perfect - meaning there are some black and hispanic kids who are extremely advantaged, and lots of poor disadvantaged whites. But it works at a system-level - systems like the schools, the criminal justice system, and the labor market consistently act to put whites in advantaged positions relative to blacks thru networks, resources, opportunities, and sanctions.
In recognition of this, we have implemented small-scale, often superficial policies that attempt to mitigate the pattern of systematic disadvantage experienced by nonwhites (I'm being general here, as the circumstance of different groups and their histories in the US are entirely different). Aff action is an example of such an attempt. It is not perfectly efficient, and there are lots of examples of people getting an edge who don't need it, and people who deserve an edge but don't get it. But categorical inequality or policy is never perfectly efficient.
There are two bases for opposing it. One is to deny that blacks or hispanics are at a disadvantage relative to whites in a wide range of systems in our society. To those making this argument I would just suggest that you read more. I didn't fully get how this works until I started reading a tremendous amount of rigorous research on it. Approach the research with an open mind.
The second basis for opposing it is that it is not a great system to counteract persistent categorical inequalities. I have more sympathy for this argument. It is not efficient at all, it leads to cases of individuals who haven't been disadvantaged getting a boost in the admissions or hiring process, and it leads to some very deserving people getting skipped over for reasons that, on a surface level, seem seriously unfair.
For those who oppose this particular mechanism of mitigating categorical inequality, a serious question: What should replace it? i.e. if we acknowledge that inequality is typically organized along categories, and we acknowledge that race remains an independent and important category, then what system-level changes would you make to mitigate race-based inequality?