Nobody (well, very few people) "self-identify" as authoritarian. It's a loaded word, obviously. You have to look at their actions and ask "is this increasing liberty, or decreasing it?" People who openly advocate suspension of due process, limiting freedom of speech, abolishing freedom of the press, etc. are authoritarians regardless of how they identify themselves.
Also, your view of Libertarians is wrong, or at least is limited to a small subset of the group. If you read online Libertarian forums and such I'm sure you'll run across a lot of that, it IS the Internet after all. As a matter of every day policy, Libertarians that actually run for office believe in a sort of idyllic utopian future which we will never reach, but try to get there one step at a time anyway. If asked about gay marriage, for example, most Libertarians I know will start with "I don't think the government should be in marriage at all", but then when queried further will follow up with "but if that's unrealistic at this time, then the very least the government can do is apply the same rights to all citizens equally" and will vote for pro-gay marriage laws that come down the pike. We believe in a way things should be, but (unless it's a teenager online who's just discovered Libertarianism for the first time) also understand that humans aren't perfect so we'll never get to perfection. Best thing we can do is try to increase liberty as much as we can where we can.
Kind of like, oh, all other political ideologies. None of them are perfect solutions. People still strive for it anyway.