Libertarianism is based on the "Non-Aggression Principle" (the NAP), which means that you have the liberty to do whatever you want, so long as you don't initiate force or fraud against another individual, or their property.
Non-aggression is not to be confused with pacifism. So long as you don't initiate force, you have the natural right to violence in self-defense. Just not to initiate aggression against another individual.
Disproportionate violence in "self-defense" is obviously also a type of aggression (an initiation of force), so chopping someone's feet off for accidentally stepping on your shoe is obviously not a right.
Libertarianism doesn't care if you choose to form a workers' co-op (à la Pierre-Joseph Proudhon), a communist commune (à la Kropotkin), or otherwise enter into any voluntary arrangement or contract -- such as *free trade commerce* (à la Ludwig von Mises), loans, employment, etc -- so long as any of these arrangements are voluntary.
Specifically, libertarianism doesn't give any exception to the 'NAP'. Not to gangs calling themselves "government". Nor, to "democracy," or some mythical "social contract," or any other type of so-called "greater good."
The Individual -- and individual liberty -- is not a means to any end; Consent is the means, and the end, to any legitimate social endeavor.