There are lots of good arguments against libertarianism. I have collected some of them into a very long document which remains the most popular thing I've ever written. But when I hear liberals discuss libertarianism, they very often head in the same direction. They make a silly face and say "Durned guv'mint needs to stay off my land!" And then all the other liberals who are with them laugh uproariously. And then when a real libertarian shows up and makes a real libertarian argument, a liberal will adopt his posture, try to mimic his tone of voice, and say "Durned guv'ment needs to stay off my land! Hahaha!" And all the other liberals will think "Hahaha, libertarians really are that stupid!"

This is an interesting example, because there is an entire subreddit of libertarians doing the exact same thing, making fun of strawman versions of anti-libertarian arguments just to train themselves to not listen to the actual arguments.

http://www.reddit.com/r/whowillbuildtheroads/

It's interesting to see the exact same technique being used as a thought-killing device by people on both sides.