Just to clarify, there is a simple general principle at work: the government should provide only public goods (1). The main dispute among libertarians is which goods qualify as public goods (e.g., is fire protection public or private?).

(1) A public good is one that is non-rivalrous and non-exclusive. Protection from commies is a public good (a dead commie isn't robbing you or me). Cheese fries are not (every fry I eat is one you can't).