The legal concept of disparate impact presumes a uniformity of intelligence and industry across racial categories against which the "disparate" or "adverse" impact of racism stands out, as if in relief. Of course the concept operates from the universal misconception "talent must be distributed equally", and merely gives a name and legal authority to conventional wisdom that holds racial inequality from wealth to incarceration to be a reliable and shameful measure of racial bias.
A useful concept of disparate impact could have real value if it was only allowed to exist: any law, policy or social phenomena will have predictably disparate impact across a diverse population. An equally applied law will have unequal results. Social change has wildly disparate and adverse impact; the sexual revolution affects the working class a little differently than it affects the elite that writes its propaganda, for one instance. Disparate impact can have huge, even evolutionary implications, it would seem. Understanding it is another necessity we deny ourselves for political correctness.
Rhetoric has a disparate impact. Smarter groups of people are better equipped than others to critically assess the dominant narrative of the moment. They're also more forgiving of hyperbole and less in thrall to emotion, all else being equal, than the less intelligent. And no group is less equipped in this regard than black America. Feeding them this relentless tale of white rapine and plunder is historically irresponsible.
Black Lives Matter is partly a reaction to the disparate impact of white norms of behavior. BLM seeks relief for blacks from these oppressive norms. It gropes toward something like a general legal double standard for blacks, enforced by a federal bureaucracy, using the Orwellian language of equality and justice. Attempts to shame BLM with black-on-black murder statistics are pointless because the cliche is true: BLM isn't really about black lives. But it is about something. It's about black American autonomy. It's an inchoate revolt against white norms.