I understand the indignation, but the cure doesn't seem workable.
First: companies never want employees to know what other employees make. This is counterproductive as it never helps the corporation - it only makes labor costs higher since no one ever advocated for a pay cut to decrease the average on "their side" - sex or whatever.
Second: Even if averages were the same, there would still be complaints about he/she being paid more than they're worth. Publishing averages forces companies to have to answer difficult, if not impossible, questions on why anyone is below average. It also introduces a mechanistic quality to pay - much like past Japanese salaryman views on "lifetime earnings". Is this really beneficial, especially given that nobody has lifetime employment?
Third: I am fascinated to see how this dynamic plays out, should these precedents get set. Male/female must have the same averages. What about married/single? gay/straight? female gay vs. male gay? Hispanic straight male vs. Asian trans-sexual (to) female?
What if one high paying member of a given demographic quits, and drops the average of that demographic significantly - should someone else be bumped up to compensate?
Could be a great jobs program for Maths PhDs to try and balance all of the demographics into a "fair" average.
Equitable pay is absolutely a problem, but I really don't see how focusing on averages helps.