Re: All else being equal...
That is the point of the argument. There is an argument that white males are paid more because of a false perception that they are worth more even when there is evidence that their female counterparts or minority counterparts are just as good.
This is exactly what an unconscious bias leading to direct or indirect discrimination is. Due to it being less overt and many companies, commentators or individuals not believing or accepting that either this is the case or that it is a possibility means that the wages and bonuses of these groups is lower.
It is difficult to produce effective trials within a single organisation to support this. However blind CVs with names, gender defining traits etc removed have shown a greater bias towards discriminated groups.
Maternity leave when taken by a single female has shown to have a greater impact on the career and pay of women than the same period of absence by a male (for instance due to a period of travel, unemployment or health).
Therefore thoughts will turn to whether females or other discriminated races are genetically or culturally poorer at jobs than males. Significant amounts of evidence based on like for like schooling would suggest this is not true and so perceptions around that are already showing evidence of prejudice and bias.
The arguments stated above generally have looked to reaffirm inbuilt bias to support an internal view (most likely around a group that has similar characteristics to the accused) rather than support an alternative argument.