I'm pretty sure I've explained it in a post above.
The number of self proclaimed libertarians who still demand that marriage is (only) between a man and a woman, weed should still be illegal, and call for US intervention at every foreign runny nose is mind blogging. There's a severe disconnect between "Libertarianism" and what its "followers" actually practice.
Hence, selective libertarianism.
Well, it does confuse things when Tea Party members claim to be libertarian when they themselves have no clue what that means. They seem to think that it means lower taxes and the ability to own guns. I think some of them even think it has something to do with "state's rights" which is pretty baffling.
But that aside, libertarianism is an ideology. No ideology in the history of mankind has been perfectly instituted, practiced or even really agreed upon by more than three people. I've always said in regard to libertarianism, you can't get there from here. Meaning, it's not about electing a couple Libertarian party members and next thing you know we're living in a Utopian paradise. Libertarianism is not a patriotic position, in my mind. It would require the complete dissolution of the U.S. government. And honestly, at the present time, it's not worth giving up what we have to establish an ideological experiment in libertarianism.
I think the very worst thing that could happen to libertarian concepts is that some yahoo (or group of yahoos) calling his or her self a libertarian gets elected and starts implementing libertarian policies piecemeal. It would be doomed to failure and libertarian concepts would be laughed out of existence from that point forward.