What you are not understanding is this:
First, examine a very simplified definition of libertarian:
- Someone who advocates that people should be free to express themselves, their ideas, etc as they like.
- Someone who believes in the doctrine of free will and the power of self-determination.
Society requires goventment. It requires rules. Otherwise there is only chaos, as few wills conflicts with each other with no mediator. Conservatives (and largely moderates) believe that the government should take a stong role in protecting the structure of society and in protecting the people as a whole. Liberals believe that government should shut the fck up, unless they need the government to work against itself to make itself shut the fck up or make others (conservatives) shut the f*ck up. This is where libertarianism comes into play.
The libertarian agenda is one that says, “I belong to myself.” This is essentially correct, but in the larger picture, it is volatile to civilization’s requirement of meadiation and government. So while a libertarian says, “You (governement or individual) can’t tell me how to run my life.”, they also say, “If you try to run my life, I’ll use you against yourself to make you not able to run my life.” The economic agenda of libertarianism says, “I have a right to what pleases me. You can’t stop me from having what pleases me, and if you try to stop me from having it, or if you try to have something that pleases you that limits what I can have that pleases me, I’ll use you against yourself to make you no longer able to do that.” This economic freedom is contrary to insuring economic prosperity, because it places prosperity in the hands of those who are most able to obtain it, instead of the ideological condition of everyone having prosperity because they can chose to get it. The problem is that prosperity does not magically spead itself out evenly amongst everyone. The energy required to insure prosperity for the whole opposes the right to not have a concept of what is required for prosperity imposed on the individual, and this relies on government intervention, because without it, the ideological fee economy of the world prospers no-one.
A libertarian says, “My income is mine. You can’t tax it.” Conservatives say, “If I don’t tax it, I can’t protedt your rights and your freedom to persue economic prosperity. I’ll be broke, and can do nothing for you.”
The libertarian says, “I want to be able to buy anything I want from anywhere in the world.” The conservative says, “I don’t want people to be able to buy anything they want, because if they can, they will buy things which are bad for us all, and they will buy things from countries that we don’t want to do business with or in a way that is not good economically for all of us.”
The essence of all of this is that libertarians demand freedom where freedom conflicts with individual rights. The activism of libertarianism is almost ideologically hypocritical, because activism in the government is discouraged unless it is for the purpose of discouraging activism.
The basis of libertarianism is a role against the activism of government and the rule of the majority over the individual. Since the role of government and the voice of the majority is largely held as a virtue by conservatives and most moderates, this makes libertarianism left-wing, because it is opposed to the right-wing doctrine of government and majority having power over the individual by any considerable measure.
I hope this helps you understand why libertarianism is left-wing doctrine.