Sounds to me like a vote for a guy who isn't your guy is a vote for your guy's main competition. Seems presumptuous. An Obama supporter could say the same thing. It's math. If 11 people vote, 5 for the R and 5 for the D, the last guy voting for an independent doesn't make the D win. You're operating under the premise that everyone should come to the conclusion that Romney is the lesser of two evils. That may be the case in your opinion. In someone else's it may be that they are pretty much equivalent.
Tell me one thing Democrats have done in the past 4 years that the Libertarian party stands for.