I'm not so sure that libertarianism comes from a leftist mindset since leftists are statists who view the state as their salvation, and if not salvation, they view it as their guide to the exclusion of all other sources.
Really? What about General Franco and General Pinochet who used the State for moral means? By your definition they would be "leftist" nevermind the fact they fought Communists in their own countries. See while Rothbard and Mises were blabbering on and on about the "evils of Marxism" while at the same time saying that any war against Marxism is "evil" these Catholic soldier patriots cleansed their countries of Marxism. That is not to say that I can really defend the Cold War since America's side was full of Cold War liberals, ex-Trotskyists, and Jews.
Libertarianism is the idea of the freedom of man from the state and from state coersion.
Exactly, it is the freedom of man to do what he wants in their world. It is the very defintion of democracy, the rule of the masses. It unbinds the individual from the State which makes him have no love of nation. That is why the free trade mentality is all about the freedom for business to do what it wants and disregard national interests. The idea of the unbridled market again leads business to do what it wants and ignore the common good of the worker.
Libertarian is a classical liberal philosophy, but it predates the enlightenment (by a lot).
I could cite Smith, Kant, Codben, Mill, Bastiat, Voltaire, etc. who all seemed to support this mindset you speak of. One can even mention FDR, a liberal by heart who was a free trader and used World War II to let America rule the world and spread freedom and democracy over the world. Another thing about liberals and libertarians is that they are very anti-religious and see their worldly paradise of open commerce as the salvation of mankind erasing hatreds, borders, and nationalities. As for myself and my political philosophy Christianity is the fabric of society.