You are making the mistake of conflating atheism with Humanism.
They are not the same thing.
Even if it’s true that all Humanists are atheists (which it is not), atheism does not denote any particular philosophy or world view. Not even naturalism per se.
Atheists may be Humanists, Nihilists, Communitarians, Owenites, socialists, Fabians, Libertarians, all sorts of categories without God belief.
Humanism is a philosophy. Not all atheists are Humanists. There in lies the confusion.
I see two distinct types of Libertarians in the USA where the Libertarian Party, Randist Objectivists, Reason Magazine, and the CATO Institute predominate.
One is free market fundamentalism. The rigid belief that unregulated economic markets and firms will adjust themselves to buyers and sellers in such a way to benefit the overall good of society.
A liberal would argue that the government has a role to play in markets and the economy.
This is something that gets propertarian Libertarians and Objectivists all steamed up.
I don’t think that Michael Shermer is of that type. He surely can’t be that closed minded or rigid!
I think Michael Shermer is of the social Libertarian type—a laissez faire understanding of ethics and morals.
In the late 60’s, the expression was, “There should not be laws regulating the morals between consenting adults” and with that the attitude that individuals should be free to explore the world for themselves as long as they didn’t force themselves on someone else. (Which, indirectly, monopoly corporations do.)
Of course, with the Libertarian Party, those two Libertarian concepts are often shared by individuals. Thus some Libertarians are both social libertarians and market libertarians.
In Europe there is a left libertarianism, which is out of the anarchist tradition and has anti-capitalist tendencies.
Chomsky, an early anarcho syndicalist has spoken on this.
Chomsky refutes “libertarian” “anarcho”- capitalism
LISTEN !!!: http://www.youtube.com/watch?v=RxPUvQZ3rcQ
The Libertarian Party and Objectivists have distorted the meaning of Libertarianism and turned it into a right wing creed that pretends to be for freedom, but in reality is for freedom of the capitalists and property owners.
Chomsky: “If terms have lost their meaning it becomes impossible to talk.”
Gary the Grouch