Who was arguing for using it as a proxy for irrationality?

The thug abusing the karma system, for one. Unless that person knows he's trying to silence people for reasons unrelated to rationality.

I will point out again that there is no concrete evidence that AA is economically inefficient lot alone highly so.

Yes, the arguments for AA are somewhat muddled...as are the arguments again and every other argument in politics. Politics isn't a science. But believing in one typically muddled argument isn't 2+2=5 irrational.

This seems an unfair response to me - TheAncientGeek offers a standard argument pro-AA while admitting they haven’t studied the issue in detail. You attack the response on grounds that an AA supporter could rebut without ever contradicting themselves (i.e. “It isn’t collective justice, it compensates for individual inequality of opportunity (unless, say, you choose to define a progressive income tax as ‘collective justice’ in which case I do support collective justice)”, “It applies to certain minorities and not others because of the size of the disopportunity facing them (discriminatory social structures don’t distinguish between recent immigrants and descendants of slaves, but they do appear to discriminate between black African and white Irish)” and “It isn’t economically inefficient, and might even be economically efficient”).

The next paragraph contains an argument for AA which I support which I think proves there is at least one rational argument for AA. If it is important to you, I can also defend my position to prove to you it is not obviously wrong (although I hope the argument alone will be enough). If there is a rational argument in favour of AA, then there must be at least one utility function that makes supporting AA rational (in the same way that a utility function which really REALLY values ants might rationally choose to try to ban glasses so children can’t use them to burn ants). I don’t agree with TheAncientGeek’s starting premise that we should therefore suppress research into race, but I think it is important you don’t base your conclusion on a faulty premise (“AA is obviously wrong”).

This 2005 paper published in The Journal of Economic Education gives the result of an experiment where participants were randomly assigned a colour (‘green’ or ‘purple’) and given the following information (I’m paraphrasing badly to ensure I remain brief, please consult the paper for the actual protocol): “You are allowed to get education, which costs £1. You then take a (simulated) test where your score is randomly picked from 1 to 100, but if you bought education the score will have a small bias towards the higher end. ‘Employers’ (other participants) will then choose whether to ‘employ’ you. They only know your colour and your test score. If they employ you, you get £5. If they don’t, you get £1. If an employer picks an individual with education, the employer gets £10, otherwise they get nothing.” I presume the experiment was then iterated an unknown number of times to prevent gaming, but I can’t find that in the paper. Clearly, the socially optimal outcome is that everybody gets education and the employers employ everybody. However, individuals can earn the full £10 rather than a net £9 by gambling on the employers being over-generous and picking them even though they didn’t get education.

By chance, the ‘purples’ happened to be under-educated in the first round, which meant some purples who got an education decided not to waste the money next round. This therefore compounded the effect, to the point where new purples realised there was no point in investing in education, so even some free-riding greens couldn’t prevent employers betting on greens (even if the green score was lower than the purple score). If the society in the experiment were allowed to implement AA they would; it would be hugely more economically efficient to remove the pro-green bias and both encourage purples back into education and force greens to keep up their initial levels of education and not ‘free ride’. The experimental confirmation that AA can be economically efficient is reason enough to support such policies, but I think they would be more effective in the real world compared to the experimental world; for example, two contradictory opinions are likely to lead to more economic progress than two homogenous opinions, and this cultural bonus is not modelled in the original experiment.