An intelligent response.
Party leaders are not as ideologically "pure" as you would like to believe. They are politicos just as much as John McCain is.
If a libertarian doesn't marginalize himself by labeling himself a Libertarian, he has a fairly good chance of winning office -- probably as a Republican. If all the registered Libertarians vote for him, he may get 1% of the vote -- and I'm presuming that the larger objective is to see the triumph and fulfillment of their ideas -- rather than that they just like to hear themselves talk, so that they can be like the lib/left/Dems who enjoy their presumed moral and intellectual superiority in these matters, while talking to no one.