I think you misunderstood my point. What you're referring to as "libertarianism" and "the Libertarian party" is what I referred to as "American libertarianism."
I don't believe true libertarianism exists in the USA. I agree with your point that the Democratic party most closely aligns with the theory of libertarianism. It sounds like you agree with the point I was trying to make, but maybe misinterpreted it.
Edit: I want to add that the Libertarian party in America doesn't follow the principal of non-aggression as I understand it.