A more full throated, conservative/libertarian defense is possible: To believe in Freedom is to believe that discrimination, by itself, without government support, cannot stand. If you and I have competing firms and you are unwilling to employ or serve a particular minority, that gives me sustainable competitive advantages -- wider access to talent and markets. In a truly free market, given those advantages, over time, my firm will crush yours. That, in practice, it does not always seem to play out this way, points to market warping Government intervention (today in the form of a failing monopolistic education bureaucracy and regulation-as-barriers-to-entry) sustaining discriminatory inequality, not to the limits of Freedom.
No ideology survives the collision with real-world politics perfectly intact. General principles have to bend to accommodate the complexities of history, and justice is sometimes better served by compromise than by zealous intellectual consistency.
This was all that Rand Paul needed to admit...
This argument, to me, seems politically viable as it re-frames the question from "Do you support discrimination or not?" (we all here agree not), to "Do you believe in Freedom?" It is naturally resisted by progressives for whom freedom is not found in, rather from, free and fair markets, and by politicians, for whom the sacrifice of principle is second-nature, but should be naturally embraced by, for example, conservative columnists.
That it is not, I think, reflects an increasingly unhealthy infatuation with an overly fixed view of culture. In their heart, I suspect, they believe that racial discrimination will persist even in free and fair markets, because, they believe, disadvantaged minorities posses and perpetuate an inferior culture.
The concept of "culture" is most properly politically employed to trace the limits of anyone's ability to meaningfully understand the deeply complicated webs that structure a society, and by extension, point to the dangers of hubristic government policy. But to believe in Freedom is to see in American history ample evidence of how malleable and ever-changing "culture" can be and how people, left to their own devices, lift themselves up.