If we were to treat the notion of “colorblindness” as the animating principle of the Constitution, the law, and the very concepts of justice and quality, we would thereby concede the moral, ethical, and ideological debates to those who assert that our interpretation of the world must be based, one way or another, on race. Instead, we should regard liberty, not “colorblindness,” as our highest ideal.
I’m not a real conservative but I’ll take a stab. I don’t think the author is praising natural inequality, merely recognizing its existence and that at least some of the unequal outcomes we observe are a result of it (not that this precludes other causes). As far as equality of humanity I think the idea is that humanity is just an innate, yes/no property of humans and doesn’t depend on every member of the species being identical or that an individual achieve something like a certain score on any of the other attributes that separate us from animals. Perhaps it is arbitrary to draw the borders of humanity where we have, but as you pointed out anything else is a slippery slope.