OK, all that said, I thought that Yglesias's wording here is a bit strange (my emphasis added):
I would note that apart from contemporary racial issues, something that links the mentality of today’s right to the mentality of the slaveowners and segregation proponents is the white southern political tradition’s very partial and selective embrace of majoritarian democracy. As long as national institutions are substantially controlled by white southerners, the white south is a hotbed of patriotism. But as soon as an non-southern political coalition manages to win an election—as we saw in 1860 and in 2008—then suddenly the symbols of national authority become symbols of tyranny and the constitution is construed as granting conservative areas all kinds of alleged abilities to opt out of national political decisions.I'm going to cry foul here. Make that patriotism, or the United States of America, or the Constitution and he's got a point. But I don't think that majoritarian democracy is the issue here. After all, heath care reform successfully jumped through every Madisonian, anti-majoritarian hoop that Republicans could throw at it -- and Republicans didn't accept that, either. Indeed, I don't think it's fair to even say that the "white southern political tradition" is selective in its embrace of democracy, in general. The core Anglo southern complaint (to the extent that we want to take it seriously as separable from race -- and it is possible that something derived from attempts to preserve racial domination could yield something separable from it) basically boils down to: Who are you (the United States) to tell us what the law should be? That's not about democracy; it's about sovereignty. The thing to get from it is that the Anglo south is actually not very patriotic, not that Madisonian democracy is racist (not that Yglesias said that).
The larger point here is that it's important not to allow selective use of general political ideas in odious political contexts prevent us from seeing those general political ideas clearly. Yes, "states rights" was code for white supremecy, even if some southerners honestly didn't realize it. That doesn't necessarily mean that decentralized governence is an inherently bad, or inherently racist, idea in a very large democracy. Nor does the history of filibusters as it actually was mean that majority rule is always best. It is evidence: one bad fascist dictator may not be proof that fascism is a bad idea, but once you get a few more...well, one starts to add that to whatever purely theoretical arguments are deployed against fascism. But it's only evidence, strong or weak, and it's perfectly possible for a very good system to produce terrible results. That's especially true, in my view, if one really believes in democracy, because in a true democracy there's always the possibility that perfectly democratic decisions will also be perfectly awful.
(That last point doesn't, by the way, really have much to do with Jim Crow; a polity that does't give full citizenship to large numbers of people because of ethnicity or other demographic traits really isn't much of a democracy, and in particularly decisions made to discriminate against the very people who are disenfranchised are in no way democratic decisions. It's a little tricky to find the correct words to describe the situation that prevailed in the US prior to 1965, but full and complete democracy would be the wrong words).