Holy hell, I've better things to do today (such as work) than engage in a tête-à-tête with you on this topic. I don't disagree with anything you write above--my GENERAL point (and no I don't care to take more time to give specific examples, so if you don't like it, tough *******) is that, as a GENERAL rule, groups who possess power tend not to relinquish it voluntarily . The US has a existing power structure that is largely male and largely white, which allows those in power (again, largely male and largely white) to allocate economic resources to its allies (again, largely male and largely white). Increasing the political, social and economic power of blacks, women or other minority (traditionally marginalized) groups inherently diminishes the power of the entrenched power structure where it comes to allocating a set of fixed (in the short to medium term) economic resources, and will thus be opposed by the members of this entrenched power structure. I believe my argument rests on valid grounds, but if you disagree, that's perfectly oky doky with me.
Edited to Add: If it were so obvious that allowing traditionally marginalized group an equal seat at the table along with traditionally powerful groups is a win-win (and in the rational self-interest of powerful groups), one must account for why this hasn't happened yet, and why it is only happening gradually and often in fits and starts. There are probably many contributing factors to this, but a reasonable hypothesis is that one factor is that powerful groups tend not to willingly relinquish power, which power allows them to allocate scarce economic and political resources to their allies, so that they and their allies can continue to capture, among other things, economic rents. Your theory can't account for the pervasive existence of anomalies, while I'm trying to propose one hypothesis as to why such anomalies might exist.