When an aide to Kentucky Sen. Rand Paul was recently revealed to have a history of badmouthing Abraham Lincoln and promoting secession, some conservatives reacted with dismay.
The divide is between so-called "neo-Confederates" and the "cosmotarians" or "liberaltarians" (all disputed terms) who oppose them.
Cosmotarians see the neo-Confederates as an embarrassing stain on libertarianism; neo-Confederates in turn see cosmotarians as intolerant, hypocritical and pro-war.
"These groups are usually at each others' throats more often than not," said Reason magazine editor Matt Welch.
Reason is firmly in the anti-neo-Confederate camp. In 2008 they reported on the racist newsletters put out under Texas Rep. Ron Paul's name and criticized the presidential candidate for allying himself with that strain in libertarianism. In response, they received scores of angry letters accusing them of selling out the movement. The neo-Confederates are largely centered around libertarian author Lew Rockwell (who worked with Paul and is widely suspected to have written the offensive newsletters), his website LewRockwell.com and his think-tank the Ludwig von Mises Institute.
It's difficult to police any political movement -- but especially one that prides itself on championing freedom of speech and the marketplace of ideas.
"We don’t have a pope. It’s very hard to excommunicate anyone and make it stick," said Jason Kuznicki, a research fellow at the Cato Institute who has argued with some of the neo-Confederates online. (He calls it a "bizarre experience.")
And there are some ideological similarities that explain the gravitation of the anti-Abraham Lincoln crowd to the pro-liberty movement. Libertarians often support a person or political group's right to secede peacefully. America was founded, after all, on a secession movement). But most will say that seceding so that it can enslave an entire race is not by any stretch of the imagination libertarian. Individual freedom easily trumps "state's rights."
Libertarians also pride themselves on their open-mindness, and the movement is made up of people who have been dismissed by the political mainstream. That can make libertarians tolerant of views they find personally repugnant.
There are contrarians who criticize Lincoln's use of federal power and argue that the South had a right to secede -- but have no love for slavery or the Confederacy. Libertarians are anti-war and in favor of market-based solutions, and some argue that even though slavery was abominable, it would have ended for economic reasons with far less bloodshed if the North had allowed the South to secede.
"Though I think Lincoln was the worst tyrant in U.S. history and his war was illegal, immoral, unconstitutional, I do not think the [Confederacy] was some quasi-libertarian bastion of freedom or justified," said Stephan Kinsella. "The real enemy is, as always, the State -- whether it be the USA or the [Confederate States of America]."
That thread of thinking makes it hard to know where to draw the line when some self-described libertarians edge over from criticizing the Union to celebrating the Confederacy.
"I think it's to our advantage to try to keep as large a tent as we can, but I think at some point you have to say, that set of ideas is not okay," said Steve Horwitz, an economist at St. Lawrence University. "Where that lies on this issue is very tricky."
But some libertarians see the disagreement as an intellectual one with no racial agenda.
"Their simplistic approach to the Civil War, if it's driven by anything, I think it's driven by an excessive commitment to libertarian principles rather than underlying racism," said San Jose University economics professor Jeffrey Rogers Hummel, who wrote an anti-slavery, anti-war study of the conflict.
The most recent flap comes at an awkward time for Republicans who trying to build their own big(ger) tent. The party wants to keep the libertarian-leaning wing on their side (witness the establishment support for Sen. Rand Paul's drone filibuster) but have to be careful not, in so doing, to embrace policies or views that would alienate large swaths of the country.
Just a few weeks ago, National Review editor Rich Lowry -- the author of a new book on why the GOP should re-embrace Lincoln -- wrote an editorial condemning "the rancid Abraham Lincoln-haters of the libertarian right."
And Rand Paul went to Howard University to argue that the party of Lincoln hasn't changed. At his side at that event -- Jack Hunter, the "Southern Avenger." There's no sign that Paul plans to fire Hunter, who appears to have given up some if not all of his controversial views.
All of which is a sign that this tension within libertarianism is not going away any time soon.