This is true:
Given the relative rarity of libertarians, both in the public eye and in general, most people’s judgment of libertarianism will be based on a very small sample – often a sample size of one. If the first libertarian someone meets is a smart, reasonable, decent person, they will come away with a positive impression and possibly a willingness to explore further. If the first libertarian someone meets is a wild-eyed lunatic, on the other hand, they could easily write off libertarianism as the ideology of wild-eyed lunatics. [...]This personality thing is a problem for libertarians, even the most reasonable, articulate, non-moonbat varieties. Sampling errors aside, there's a well-recognized phenomenon wherein views expressed by people we admire and like are more persuasive merely by being associated with that person. (Mormons seem to get this, in a big way.) Friendly people are far more successful at spreading their beliefs (cf. meme theory). And libertarians, even the smart articulate ones, tend to come across as intellectual, elitist, even snobby at times (especially in person, as opposed to in the blogosphere). Maybe this is because on average, libertarians spend way more time identifying and thinking about their beliefs than people of more standard political persuasions, thus making them more conversant with political theory and/or somewhat scornful of the unthinking multitudes. Whatever the reason, libertarians (and I don't except myself here) may need to make a special effort to be approachable and friendly and, well, nice, in addition to the traits Glen identifies above.
This is why, when I talk to young libertarians about how to spread their ideas, I say they should think of themselves as ambassadors for the movement. That means, first and foremost, presenting themselves as fundamentally decent people that you would actually want to have a beer with [...].