Nick Cohen makes an important point here - that the oppressed are not necessarily more virtuous than others. I want to expand upon this. There are several mechanisms that might cause this.

One, which is most relevant to Nick's argument, is that oppression often produces stress and anxiety, which in turn can produce self-obsession and narrow-mindedness - just as hypochondriacs are bores to be around because they are forever fretting about their ailments. In his lovely book, The Moral Consequences of Economic Growth, Ben Friedman shows how for this reason bad economic times lead to upturns in intolerance and racism. Some bien-pensants are quick to accuse the white working class of being racist - but if that oppressed group can have reactionary or self-centred attitudes, why can't others?

There are three other mechanisms here:

- Ego-depletion. If it's a struggle to just get by, you'll have fewer intellectual resources with which to consider other problems. Researchers at Princeton have shown that, for this reason, the poor tend to have a lower IQ than the rich. But I wonder: might the same be true for people struggling with other oppressions such as racism or sexism?

- Adaptive preferences. One notable fact about many of the oppressed is that they are so damned quiet about it. This is because they resign themselves to their fate. As Amartya Sen has written:

Deprived people tend to come to terms with their deprivation because of the sheer necessity of survival, and they may, as a result, lack the courage to demand any radical change, and may even adjust their desires and expectations to what they unambitiously see as feasible (Development as Freedom)

- Ideology. Several well-known cognitive biases - such as the anchoring heuristic, status quo bias or just world illusion - can combine to produce an acceptance of inequality and injustice; see, for example, John Jost's system justification theory (pdf).

All of this suggest that oppressed groups need not have an accurate opinion of injustice. Many might not see themselves as oppressed, and those that do might lash out at the wrong targets - be it taking offense at silly racist talk rather than structural racism or blaming immigrants for low wages rather than various forces within capitalism.

It is of course true that one of the great problems for Marxism has been that the working class has not developed the class consciousness that Marx hoped for. But why should other oppressed groups fare any better?

Now, this is NOT to say that such groups should not be heard and should instead be represented by wiser heads such as um, well white male PPE graduates. For one thing, the more privileged have weaker incentives to fight inequality. And for another, they/we too are also prone to cognitive biases: one of the sillier inferences of the "nudge" agenda has been the idea that rulers are free of cognitive error.

Instead, we much distinguish sharply between two questions: "what do you think?" and "what do you know?" It's the latter that matters. For example, the everyday sexism project has awakened me to the troubles that women face far more than windy feminist theory has done.

Which brings me to the problem. The institutions that might give voice to the lives of the most oppressed - the poor both here and globally; women and gays in backward communities and so on - are to say the least under-developed. One of the symptoms of genuine oppression is that one's voice is not heard. When this absence is combined with the lack of mechanisms to counter false consciousness, it is small wonder that injustice is perpetuated.