They're right that ideology led the movement astray that year -- but wrong in the emphasis they put on that single data point.
You'd think, reading Jonathan Chait, that throughout American history the federal government has been on the side of anti-racism, while state governments have done their utmost to subjugate blacks. It's indisputably true that racists have often wrapped themselves in the language of states' rights, and that the cause of black equality has at times been gravely undermined by states' rights. But there is nothing inherently racially progressive about actions taken in Washington, D.C. The Fugitive Slave Act is one instance when federal usurpation of state prerogatives harmed the cause of liberty. Dred Scott would've been better served under state law too.
Writing under the headline, "Ron Paul's libertarian principles support racism," Chait asserts that the most fervent opponents of equality for blacks during the Civil War years and Civil Rights era "usually made their case in process terms rather than racist ones. They stood for the rights of the individual, or the rights of the states, against the federal Goliath. I am sure Paul's motives derive from ideological fervor rather than a conscious desire to oppress minorities. But the relationship between the abstract principles of his worldview and the ugly racism with which it has so frequently been expressed is hardly coincidental." I am not sure that follows - it isn't as though racists are consistent in their embrace of individualism! - but put it aside.
What confuses me is the presumption that because increasing federal power relative to the states was most conducive to racially enlightened policy-making during the 1860s and again in the 1960s, the same reality holds true today. It seems to me that the opposite is more likely true.
In our time, prevailing social norms are opposed to racism; alternative centers of power like big corporations, academia, and the large media organizations are generally anti-racist; and the 13th, 14th, and 15th amendments are enshrined in the Constitution. There is no chance of repeal. The Civil Rights Act is settled law too, which doesn't mean Ron Paul shouldn't be challenged for having said he'd oppose it - just that how someone would've voted had they been in Congress back then won't impact race in America much today. There are, however, policy areas where the extent of federal power is actively contested, and other areas where federal and state policies are in current conflict, with outcomes as yet to be determined. The most consequential is drug law.
Surely it is plausible -- I believe it to be true -- that a marginal decrease in federal power and increase in state power will permit states to proceed with policies like the decriminalization of marijuana, with forward-looking states taking the lead on overdue reforms -- perhaps in much the same way that state actions on marriage helped open that institution to gays, even as anti-gay marriage forces tried to assert federal control in the guise of the Defense of Marriage Act and a proposed constitutional amendment to define marriage as being between a man and a woman.
Again, preferring state to federal decisionmaking isn't a predictor of how enlightened a given policy will be.
It is further plausible that libertarian ideology is best equipped to address the most dire current threat to an ethnic minority: the federal government's bipartisan assertion of the right to indefinitely detain folks deemed by the president to be terrorists, which understandably makes non-terrorist Muslim Americans a lot more nervous than it makes non-terrorist Christians or Jews. Libertarians are certainly speaking out against that threat more reliably than liberals or conservatives.
There is no ideology that guides rigid adherents to the right policy in every situation. One strain of libertarian ideology certainly led many of its adherents to oppose liberty expanding policies during the Civil Rights era. That was a serious failure, one that has rightly provoked useful soul-searching among libertarians. But anti-libertarian ideologues like Chait make a mistake when they presume that because empowering states has at key moments done a disservice to minority rights, the libertarian arguments calling for a limited federal government and decentralized power are somehow always bad for minorities or contrary to the cause of expanding liberty.
That Chait is blind to (or at least conspicuously silent about) the most problematic consequences of an empowered federal government today is evident from his narrative of the Obama Administration, which is utterly silent about the myriad policies Obama has pursued that undermine civil liberties, disproportionately impact minorities, and corrode checks and balances built into the Constitution. It is no comfort to the victims of Obama's excesses that Chait, who can't even be bothered to mention them, is hyper-attuned to the real and disappointing ways that libertarian ideology led many of its adherents astray five decades ago (and its paleo fringe more recently than that) -- though I've missed it if he's offered a similar critique of liberal failures on race during the first half of the 20th century, including horrific policies implemented by left-leaning icons. When Jonah Goldberg wrote a book arguing that the left's bygone embrace of fascistic policies proved the ideology to be flawed at its core, and implied that its past helped explain why we should be suspicious of Hillary Clinton-style liberalism, I don't recall Chait being a particular fan of his approach to evaluating today's ideologies.