Extremism and the Double-Standard

Yesterday Tyler Cowen blogged about an article in The National Review Online in which a claim is made that leftist books have been more policy-oriented, while rightist books have been more ideology-oriented in recent years. Because this pertains almost entirely to ideologies I oppose, I don't really have a comment on this matter.

However, Cowen's excerpting of the following passage from the article stood out to me:
People on the right classify themselves as libertarians, neoconservatives, social conservatives, traditional conservatives, and the like, and spill oceans of ink defining, debating, and further subdividing these schools of thought.
What bothers me about this is the claim that libertarianism is a form of conservatism. Those familiar with libertarianism know this to be patently false, and I commented accordingly on Cowen's blog:
Classifying libertarians as “a type of conservative” is an act of leftist propaganda, as far as I’m concerned. Leftists know that libertarianism blows a gaping hole in their entire set of ideologies *and* policies. Their only ability to respond to libertarian criticism is to engage in the ad hominem lie that libertarians are “conservative extremists.” 
Someone writing under the pseudonym "question the question" responded, in part, as follows:
My response to libertarianism is that it is ideological in the extreme and that any policy recommendations (such that they are, most are wildly overarching and short on details) are suited not for the real world but for some utopian fantasy.
Okay, Folks. This is Important.
What a double-standard that is! "Question the question" has just exposed one of the many "shabby secrets" Ayn Rand used to refer to in her nonfiction works.

The implication here is that when a libertarian proposes to eliminate, oh I don't know, the FDA, that's "extreme" and part of "some utopian fantasy." But when a leftist or a rightist suggests the creation of a new federal agency, that's not extreme at all!

We have grown so accustomed to hearing calls for new federal departments, agencies, committees, and so forth, that we no longer consider such calls for regulation to be "extreme." Yet if someone calls for the direct logical counterpoint, that person is labeled an extremist. Why?

Think about it. The opposite of painting your garage door black is not painting it at all. Why is painting it black "normal," but choosing not to paint it is part of "some utopian fantasy?"

Or perhaps the opposite of painting the garage door black is stripping all of the paint off so that it is the color of plain aluminum. You and I might disagree as to whether such a door is visually appealing, but what we cannot do is suggest that one is more "extreme" than the other. All-black is just as extreme as not-at-all-black. This is an indisputable fact of logic.

Logically speaking, the set of all real numbers from negative-infinity to positive-infinity is just as extreme as the empty set. They are nothing more than opposite concepts. If one is extreme, so is the other. If one is not extreme, then neither is the other.

The truth is, libertarians are no more extreme than anyone else. The only relevant difference is that everyone else has claimed ethics, ideology, and pragmatism as their own, and denied it to libertarians by default. We must not stand for this.