I completely agree with the conclusion--we are one species. And I don't think it makes very much sense to be proud of something that one didn't appreciate some positive factors. So it's quite true that we all have an African origin, and although my more recent ancestors were mostly from Europe, I particularly appreciate my African heritage because this is very long indeed, and is where evolution sculpted us into the amazingly capable creatures we now are. (I also appreciate my primate heritage; we have great vision, dexterity, and curiosity among other things thanks to our primate heritage.)

The subdivision of extant humans into "races" was, in the past, the result of some extremely motivated thinking, as you point out, and contains a lot of history of atrociously inhumane treatment. Genetically, none of the divisions are clear, as grouops never maintained sharp boundaries between each other. Inasmuch as there are regional genotypic differences by lineage, "white" is a race, "east asian" is a race, "indigenous American" is a race, and "black" is at least a half dozen different races each at least as different as the previous ones are from each other. And even given these genetic differences by lineage, individual genetic differences still are larger than these group-based ones. So if you put biology first, not supremacy, although there are biological correlates of some of our labels of "race", it makes little sense to use that information for anything significant because it just doesn't predict very much. So, luckily, biology has made things easy for us: we don't have huge gulfs in capability between human subspecies that force us to really confront what we mean by "human" and just how deeply we hold values of compassion and mutual help vs. hatred and self-interest. We don't have subspecies. We're on easy mode.

However, your argumentation is at best very hard to follow.

You give multiple examples of the following form: racist "white" person studies X; claims to have discovered Y; person concludes it is okay to mistreat "blacks". Quite awful.

But how does this have anything to do with whether blacks having the capacity to be racist means that "the position of shared equity on the racial hierarchy with Whites can only render a biological-genetic predisposition to explain all of their relative disparities"? The two things don't have anything to do with each other. You can be racist for all sorts of reasons; you don't have to decide that society gives the perfectly just reflection of our genetic predispositions. You could decide to be racist against group G because "G's are dumb" or because "G's are immoral" or because "G's are always mean to us" or any number of other reasons. These are attitudes, feelings. They're not truth. They don't determine why there might be a disparity on average between members of group G and those of group H.

So I don't see any danger at all in recognizing that individual racism can be expressed by people of whatever race, so long as it's true and we know what we mean by those words. I also don't see any danger at all in recognizing that institutional racism can be expressed by any institution of sufficient power and in any direction--though of course we should have no illusions about what direction it goes in the United States.

We can be prejudiced against each other for all sorts of reasons based on whatever boxes we categorize each other into: politics, race, geography, sports team affiliation, eye color, culture, whatever. We can always invent a genetic or neurological basis--look at the studies about differences between Republicans and Democrats. Heck, the basis might even be true. That doesn't mean that it's okay to be horrible to each other.

That's the real danger: deciding that the relatively modest and/or imagined and/or arbitrary differences that humans have with each other is cause for treating some people really badly. We might at different points in history draw the lines differently: if you are European but not Jewish, are Jews white? If you are San in Namibia, are Bantus on your side, or are you the "other"?

We are all African. And we all have the propensity to draw distinctions that are not fundamental and conclude that we should treat each other as enemies. An ongoing challenge, and one I hope we succeed at, is to tame our tribal instinct and embrace the overwhelming amount that we share.