Correction: The mafia as they exist today only exist because of the improper, illegitimate government we have today.
As Frederick Bastiat wrote in "The Law" there would still be a "government," but it would be infinitesimal compared to its current size, and it would solely concern itself with sociopaths who were guilty (or seemingly guilty, prior to the proper jury trial) of force and/or fraud (coercion: the initiated realistic threat of force or initiated, non-retaliatory force itself).
Voluntaryists don't oppose government. They just want smarter government; ie: self-governance in the voluntary sphere. Does every government today fall so far short of this standard as to make abolition of all governance a viable interim goal? Sure. A good case could be made for that. Historically, this places me alongside Emma Goldman, Thoreau, and Lysander Spooner.
BTW: Spooner was not an anarchist. He was an abolitionist, a libertarian, and a minarchist. The same is true of Bastiat and Thoreau.
Government is an immune system, only. When it is disordered, the republic dies, the same way a human dies when infected with AIDS or any other auto-immune disorder. The current government we have is like AIDS or cancer. But that doesn't mean that immune systems are bad. They're only bad when they have nothing in common with, or "are the opposite of," the best version of themselves.
Note: I'm a voluntaryist libertarian who is agnostic in the pointless (unresolvable) debate over re-labeling the pattern-found-in-nature that is sometimes called "anarchy" and sometimes called "minarchy,"depending on one's Historical and Scientific education level. So I can interface with people who inconsistently defend the American idea as considered by the Founders, I often call myself a "minarchist," much as Eliezer Yudkowsky does (although perhaps I'm more radical than he is).