I always found it funny that the word "libertaire" (french translation of libertarian), come from the word liberal with the word "proletaire", and is now used to qualify some members of the american far-right.
It was used to criticise liberal anarchism (Proudhon) because it was not socialist/egalitarist enough, and later inspired Marx (who built his theory of communism with anarchist fundation). So people in US that call themselves "libertarian" could change their names to "communists cousins", really.
Libertarianism is a big tent. There are right-libertarians (like the ones you describe), left-libertarians, anarchist-leaning libertarians, Randian Objectivists, etc. These camps differ in numerous ways but there's a general undercurrent and large areas of agreement.
It was used to criticise liberal anarchism (Proudhon) because it was not socialist/egalitarist enough, and later inspired Marx (who built his theory of communism with anarchist fundation). So people in US that call themselves "libertarian" could change their names to "communists cousins", really.