Both liberal and conservative thought must deal with the self evident differences amongst peoples. The key difference is the conclusion they reach, whether or not it justifies centrally mandated and enforced homogenization of outcomes.
Liberal thought blames social, cultural and economic inequities for causing these categorizations, which is exactly what Graves is doing. Then liberals can justify more centralized power to address these inequities. In their view, these inequities (and other calamities, such as global warming) are man made, and we (the collective we, really meaning them, the would be tyrants) should fix them. The collective improperly assumes the role of God. Hubris.
Conservative thought recognizes that there are God given or natural categorizations and differences. It is fitting and proper that there will be a wide variety of outcomes, depending on our individual capabilities, energy, resolve, genetics, upbringing, situation and a bit of luck. We each individually have the responsibility to be the best we can be. Central government has a limited role to provide for the common defense and provide a fair legal and economic framework. Fairness not measured by equal outcomes, but by equal opportunity, within practical limits. A moral authority beyond our understanding, or at least beyond our power to manipulate, determines the outcomes.
Of course. And they are not biologically defined in most cases (except in genetic diseases or conditions -- but that's not what you mean).
As a side note, for perspective, this is a basic teaching of the Bible as well that the differences you speak of and I agree exist are not biologically defined.