> this is a hard truth to accept for people of any political persuasion

I think it should be welcome by people of all political persuasions. To explain inequality, the Right tends to assume epidemic laziness (wanton self-destructive behavior) while the Left tends to assume epidemic racism and hatred -- neither of which is particularly nice. We can still choose whether we want equality of opportunity or equality of outcomes, but we can make that choice with compassion and have a much better shot at effective policy to support it when we acknowledge the truth.