The libertarian answer in this instance is that property rights trump civil rights, and that the state should prioritize enforcing those.
Gary Becker summarized the literature on the economic effects of discrimination as part of his 1992 Nobel Lecture. Libertarians could emphasize one aspect of Becker’s writing:
in a world with constant returns to scale in production, two segregated economies with the same distribution of skills would completely bypass discrimination and would have equal wages and equal returns to other resources, regardless of the desire to discriminate against the segregated minorities ... A literature has developed on whether discrimination in the marketplace due to prejudice disappears in the long run.
A fair reading of Becker’s Nobel Lecture, however, would note that he believed that private discrimination by the majority does injure the minority. Is this the kind of economic policy Tea Party types such as Rand Paul are advocating?