"Acceptable" is a weak word. It's not going to be acceptable to a court that has decided what the law is and ordered you to follow it, and Volokh isn't trying to say that it is. He's really only asking us to look at the Kim Davis problem from the perspective of those who think that the acceptance — there's that word again — of gay marriage is an evil on the scale of slavery or Nazi Germany.
Not that we have to agree with that view, but the question is whether the (possibly oath-based) proceduralist argument (“do your job or engage in revolution, but if you do that you have to quit, because OMG the oath”) should carry any logical weight with adherents of that view. While I think acceptable resistance against Nazis differs from acceptable resistance against liberal democratic governments, the reason I think that has nothing to do with oaths, and it’s not clear to me how an oath-based theory would successfully distinguish between the two situations.Also at Volokh Conspiracy and getting much more attention (ranking high on WaPo's most-read list), is Eugene Volokh's "When does your religion legally excuse you from doing part of your job?," which focuses on law as it is, as opposed to morality, revolution, and disobedience.
Bottom line: I’m fine continuing to criticize Davis on substantive moral grounds. And I’m fine showing why Davis’s actions are illegal under the positive law; but once you get to the point where you’re making the illegality serve a normative goal, you have to confront issues of legitimate disobedience, and I’m not sure that a purely procedural (“quit or do your job”) argument will work to exclude Davis’s “keep your job but follow your ideals” strategy of disobedience.
I'm using my tag "civil disobedience," even though Sasha Volokh eschews the adjective and speaks only of "disobedience." I think "civil" is inappropriate because Davis is not a citizen resisting the government. She's a government official. "Civil" denotes a connection to ordinary citizens. There's something much fishier about someone working within the government, not following the rules.
Should we accept (there's that word again) IRS agents resisting tax-exemption applications from groups that represent politics they think are evil? Think of resistance from the inside by police officers, teachers, judges, social workers, prison wardens, and the rest of the immense cast of characters that make up the government and against whom we, the citizens, assert our civil rights.
ADDED: For what it's worth, here's the (unlinkable) OED entry for "civil disobedience":
civil disobedience n. rebellion of the populace against a governing power; (in later use) spec. refusal to obey the laws, commands, etc., of a government or authority as part of an organized, non-violent political protest or campaign.