Consider the period between 1930 and 1964. What priority did libertarians give to the abolition of Jim Crow laws? How many even considered the issue worth specifically addressing?
Towards the end of that time period, of course, Milton Friedman's Capitalism and Freedom was published (in 1962). So I checked through the whole thing. I'll give the details shortly but here's my bottom line: Friedman did consider the issue worth addressing and was, of course, on the right side of the issue. That is, he opposed such laws. However, he did not give it a high priority. At the end of his second chapter, "Government in a Free Society," Friedman listed 14 then-exisiting restrictions on economic freedom that he thought should be eliminated. Among them were many things that disproportionately hurt black people: minimum wage laws, military conscription, and Interstate Commerce Commission restrictions on trucking. But he did not call attention to that differential hurt (although later in the decade, on the minimum wage law, he did) and did not list Jim Crow laws per se.
As I noted above, though, it was clear that he was against such laws. In his chapter, "Capitalism and Discrimination," for example, he wrote:
The Southern states after the Civil War took many measures to impose legal restrictions on Negroes.
It's clear from context that he opposed such restrictions. Later in the chapter, he also wrote:
The Hitler Nuremberg laws and the laws in the Southern states imposing special disabilities upon Negroes are both examples of laws similar in principle to FEPC [Fair Employment Practice Commissions.]
This last requires some explanation. It is pretty certain that Friedman, who was Jewish, would not liken Jim Crow laws to Hitler's Nuremberg laws unless he opposed the former. But why compare it to FEPC laws, the predecessor of the later civil rights laws that banned racial discrimination in employment? Friedman explains that both are wrong because "they involve a kind of state action that ought not to be permitted."
So Friedman was doing two things: (1) opposing Jim Crow laws because they required discrimination, and (2) opposing laws that forbade discrimination.
Why does he give the second equal, or arguably greater, emphasis the first? I think I understand from context. Friedman was often writing to persuade young people and/or people who thought of themselves as "liberals." Just as he took it as given that the Nuremberg laws against Jews were wrong and the point did not need to be argued, he took it as given that Jim Crow laws were bad and probably didn't think the point needed to be argued. He argued, instead, the point that he thought needed to be argued to his audience: as abhorrent as racial discrimination is, it's wrong to prevent people from practicing it peacefully with their property and their workplaces. Still, I wish he had put it in his 14-point list in Chapter 2 and made it 15 points.