Sure, there are kooks who self-describe as libertarians. Certainly the Libertarian Party has a large kook fringe, but the kook percentage in the LP is no larger than that of Democrat Party. If you combine the percentage of crooks and egregious hypocrits with the kooks of the Republican Party, it’s comparable with the LP as well.
I know that’s argument by assertion. I don’t have any data to substantiate my assertions, but the argument in the foregoing paragraph is no less specious than Marty Beckerman’s criticism of libertarianism.
But I agree with Beckerman that “pure libertarian economics are galaxies away from the American mainstream”. Americans want their welfare checks, free medical treatment, free childcare (pre-K to graduate school), subsidies, prohibitions and national preeminence more than they want their liberty.
Why do libertarians always assume that anyone who is not a libertarian must want a welfare check and a nanny-state? Your criticism sort of makes Beckerman's point for him.
“Pure Libertarian economics” sounds like a return to the feudal age to me.