That's the textbook definition of a "strawman argument". You might be doing that too, but it's not something that contributes to civil discourse, so I thing we're still covered.
See my tagline. I engage libertarians almost on a daily basis. “Strawman argument”? Not even. I read their arguments for legalizing drugs, pornography, abortion, gay marriages and worse almost on a daily basis. Here at Free Republic.
As for me? I’m finding it humorous that throwing a little liberal logic in the mix here is hitting too close to home for many libertarians.