Libertarians tend to shoot down their own credibility without anyone else doing anything to them.
For instance, instead of sticking to clear facts such as "government has gotten bigger", on which open-minded people would at least hear them out, Libertarians tend to rapidly dive into the tin-foil land of lies such as "everything that government does is unConstitutional", or "everything that Republicans do is socialist", and other such nonsense.
But in the big picture, such wild-eyed, grossly misguided myths are just small potatoes compared to the really damaging flaws seen in 90+% of all known Libertarians (e.g. their poor people skills and tendancy to be overly argumentative, as well as their literal disdain for taking "baby steps" to solve any current problem - they want their Revolution and they want it all now).