From iSteve commenter jb:

… how I think liberal affirmative action supporters actually justify AA in their own heads (as opposed to the lazy “it must be because they hate white people” thinking I see so often in forums like this): …

1. We know that blacks are intrinsically just as smart as other races. (This is revealed truth. It must be so. It would be just awful if it weren’t!).

2. And yet blacks do poorly on all measures of cognitive ability. (The “achievement gap”).

3. Therefore something must be holding them down. (The legacy of racism. Stereotype threat. Socioeconomic status. Lack of self esteem. Something!).

4. The solution is affirmative action. If we can artificially place enough blacks in high positions that they do not appear qualified for but deep down really are (see point 1) then eventually they will reach a critical mass that allows them to overcome whatever is holding them down.

4a. There is no downside to affirmative action! Because we know that blacks are just as smart as whites, it follows that whatever their test scores might seem to indicate, the highest scoring blacks are intrinsically just as capable as the highest scoring whites, and are therefore guaranteed to be every bit as competent when handed positions as doctors, lawyers, professors, scientists, air traffic controllers, etc. Any evidence that suggests otherwise (including the evidence of your own lying eyes) has to be wrong somehow.

5. If it hasn’t worked yet that just means we haven’t been affirming hard enough. (We need to go back up the mountain again—this time Jesus will come for sure).

I’d add:

6. Besides, it’s racist to mention that affirmative action exists.