The thing I tell libertarians generally ... is you can't make your happiness contingent on getting a libertarian society. The struggle for liberty will never end because there are always going to be statists. There are always going to be people who enjoy security over liberty, because that's another part of the natural instinct that people have. And so the best that we can ever accomplish is keeping liberty alive.
Whether Barnett means national security or, as I assume, a personal desire for stability and minimal comfort, he assumes the classical tradeoff most famously formulated by Benjamin Franklin. While Franklin qualifies the terms of the tradeoff, warning against exchanging "essential" liberty for "temporary safety," Barnett appears to assume an innate tension between human desires for liberty and security/safety. On some level this makes sense. On perhaps the simplest level our desire for safety from violence curtails our liberty to do violence. Barnett presumably has no objection to that sort of tradeoff, though that particular yearning for security is as "statist" as any other. But the crucible of "statism," for him, puts security and liberty in conflict on more levels than he's comfortable with. But perhaps his discomfort results from an impulse to label tradeoffs in more dramatic or portentous terms than they deserve. Ultimately both "liberty" and "security" are labels. Neither exists in nature. Philosophers and ideologues may speak of natural liberty, but most if not all acknowledge the necessity of political power, which doesn't exist in nature, to secure it. To assert a tension or tradeoff between "liberty" and "security" is inevitably subjective. It would be no less objective, nor any more "Orwellian," to assert that liberty and security are one -- that liberty exists only where there is security. Of course, such an assertion begs the definition of "security," but it's always up to a body politic to define both that term and "liberty" to the satisfaction of its members. Barnett may be right, however, to suggest that no polity can ever agree fully or permanently on the terms, and that the struggle for both liberty and security will never end. It certainly must go on so long as some feel that others' desire for security of some sort impinges on their own rightly inalienable liberty, and others feel that someone else's claim of liberty makes their own lives less secure. Indeed, many feel that perpetual insecurity deprives them of liberty, while many others fear that statism makes their liberty insecure. It's probably a natural feeling in either case, and if that strikes you as sophistry, so should Barnett's words. It certainly is a zero-sum game, after all, when the terms of the debate are empty.