Libertarians are good to work with on a grass-roots level. I met a few when our conservative Republican state senator came to speak and take questions one night. I don't preach that they are throwing their votes away there, or on this board for that matter.
Hell, I voted for Ron Paul in '88, but I eventually learned that the sensible thing to do is vote third-party only in races where your candidate has run a good campaign with some backing. Save your throwaway votes for the dogcatcher's race.
Thruthfully, the only Libertarians, that I have run into, are thse on this site , and in real life, a filthy, lon haired, bum looking, seemed to be stoned or drunk ( or just insane ) , ranting man, handing out leaflets on a street corner in Chicago, in 1975 . I haven't met anyone, whilst working for a Republican candidate , on any level ... who admits to being a Libertarian ; not ever . So, I won't comment about that.
I agree with your second statement ; the one where you say that one can throw away one's vote, on the dog catcher and nothing higher. : - )